chore(release): 4.6.1

Diff: https://github.com/socketio/socket.io/compare/4.6.0...4.6.1

.github/workflows/ci.yml

@@ -6,21 +6,31 @@ on:
   schedule:
     - cron: '0 0 * * 0'
 
+permissions:
+  contents: read
+
 jobs:
   test-node:
     runs-on: ubuntu-latest
+    timeout-minutes: 10
 
     strategy:
       matrix:
         node-version: [12, 14, 16]
 
     steps:
-      - uses: actions/checkout@v2
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
       - name: Use Node.js ${{ matrix.node-version }}
-        uses: actions/setup-node@v2
+        uses: actions/setup-node@v3
         with:
           node-version: ${{ matrix.node-version }}
-      - run: npm ci
-      - run: npm test
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Run tests
+        run: npm test
         env:
           CI: true

CHANGELOG.md

@@ -1,3 +1,311 @@
+# History
+
+## 2023
+
+- [4.6.1](#461-2023-02-20) (Feb 2023)
+- [4.6.0](#460-2023-02-07) (Feb 2023)
+
+## 2022
+
+- [4.5.4](#454-2022-11-22) (Nov 2022)
+- [4.5.3](#453-2022-10-15) (Oct 2022)
+- [4.5.2](#452-2022-09-02) (Sep 2022)
+- [2.5.0](#250-2022-06-26) (Jun 2022) (from the [2.x](https://github.com/socketio/socket.io/tree/2.x) branch)
+- [4.5.1](#451-2022-05-17) (May 2022)
+- [4.5.0](#450-2022-04-23) (Apr 2022)
+- [4.4.1](#441-2022-01-06) (Jan 2022)
+
+## 2021
+
+- [4.4.0](#440-2021-11-18) (Nov 2021)
+- [4.3.2](#432-2021-11-08) (Nov 2021)
+- [4.3.1](#431-2021-10-16) (Oct 2021)
+- [4.3.0](#430-2021-10-14) (Oct 2021)
+- [4.2.0](#420-2021-08-30) (Aug 2021)
+- [4.1.3](#413-2021-07-10) (Jul 2021)
+- [4.1.2](#412-2021-05-17) (May 2021)
+- [4.1.1](#411-2021-05-11) (May 2021)
+- [4.1.0](#410-2021-05-11) (May 2021)
+- [4.0.2](#402-2021-05-06) (May 2021)
+- [4.0.1](#401-2021-03-31) (Mar 2021)
+- [**4.0.0**](#400-2021-03-10) (Mar 2021)
+- [3.1.2](#312-2021-02-26) (Feb 2021)
+- [3.1.1](#311-2021-02-03) (Feb 2021)
+- [3.1.0](#310-2021-01-15) (Jan 2021)
+- [2.4.1](#241-2021-01-07) (Jan 2021) (from the [2.x](https://github.com/socketio/socket.io/tree/2.x) branch)
+- [3.0.5](#305-2021-01-05) (Jan 2021)
+- [2.4.0](#240-2021-01-04) (Jan 2021) (from the [2.x](https://github.com/socketio/socket.io/tree/2.x) branch)
+
+## 2020
+
+- [3.0.4](#304-2020-12-07) (Dec 2020)
+- [3.0.3](#303-2020-11-19) (Nov 2020)
+- [3.0.2](#302-2020-11-17) (Nov 2020)
+- [3.0.1](#301-2020-11-09) (Nov 2020)
+- [**3.0.0**](#300-2020-11-05) (Nov 2020)
+
+## 2019
+
+- [2.3.0](#230-2019-09-20) (Sep 2019)
+
+## 2018
+
+- [2.2.0](#220-2018-11-29) (Nov 2018)
+- [2.1.1](#211-2018-05-17) (May 2018)
+- [2.1.0](#210-2018-03-29) (Mar 2018)
+
+
+# Release notes
+
+## [4.6.1](https://github.com/socketio/socket.io/compare/4.6.0...4.6.1) (2023-02-20)
+
+
+### Bug Fixes
+
+* properly handle manually created dynamic namespaces ([0d0a7a2](https://github.com/socketio/socket.io/commit/0d0a7a22b5ff95f864216c529114b7dd41738d1e))
+* **types:** fix nodenext module resolution compatibility ([#4625](https://github.com/socketio/socket.io/issues/4625)) ([d0b22c6](https://github.com/socketio/socket.io/commit/d0b22c630208669aceb7ae013180c99ef90279b0))
+
+
+### Dependencies
+
+- [`engine.io@~6.4.0`](https://github.com/socketio/engine.io/releases/tag/6.4.0) (no change)
+- [`ws@~8.11.0`](https://github.com/websockets/ws/releases/tag/8.11.0) (no change)
+
+
+
+## [4.6.0](https://github.com/socketio/socket.io/compare/4.5.4...4.6.0) (2023-02-07)
+
+
+### Bug Fixes
+
+* add timeout method to remote socket ([#4558](https://github.com/socketio/socket.io/issues/4558)) ([0c0eb00](https://github.com/socketio/socket.io/commit/0c0eb0016317218c2be3641e706cfaa9bea39a2d))
+* **typings:** properly type emits with timeout ([f3ada7d](https://github.com/socketio/socket.io/commit/f3ada7d8ccc02eeced2b9b9ac8e4bc921eb630d2))
+
+
+### Features
+
+#### Promise-based acknowledgements
+
+This commit adds some syntactic sugar around acknowledgements:
+
+- `emitWithAck()`
+
+```js
+try {
+  const responses = await io.timeout(1000).emitWithAck("some-event");
+  console.log(responses); // one response per client
+} catch (e) {
+  // some clients did not acknowledge the event in the given delay
+}
+
+io.on("connection", async (socket) => {
+    // without timeout
+  const response = await socket.emitWithAck("hello", "world");
+
+  // with a specific timeout
+  try {
+    const response = await socket.timeout(1000).emitWithAck("hello", "world");
+  } catch (err) {
+    // the client did not acknowledge the event in the given delay
+  }
+});
+```
+
+- `serverSideEmitWithAck()`
+
+```js
+try {
+  const responses = await io.timeout(1000).serverSideEmitWithAck("some-event");
+  console.log(responses); // one response per server (except itself)
+} catch (e) {
+  // some servers did not acknowledge the event in the given delay
+}
+```
+
+Added in [184f3cf](https://github.com/socketio/socket.io/commit/184f3cf7af57acc4b0948eee307f25f8536eb6c8).
+
+#### Connection state recovery
+
+This feature allows a client to reconnect after a temporary disconnection and restore its state:
+
+- id
+- rooms
+- data
+- missed packets
+
+Usage:
+
+```js
+import { Server } from "socket.io";
+
+const io = new Server({
+  connectionStateRecovery: {
+    // default values
+    maxDisconnectionDuration: 2 * 60 * 1000,
+    skipMiddlewares: true,
+  },
+});
+
+io.on("connection", (socket) => {
+  console.log(socket.recovered); // whether the state was recovered or not
+});
+```
+
+Here's how it works:
+
+- the server sends a session ID during the handshake (which is different from the current `id` attribute, which is public and can be freely shared)
+- the server also includes an offset in each packet (added at the end of the data array, for backward compatibility)
+- upon temporary disconnection, the server stores the client state for a given delay (implemented at the adapter level)
+- upon reconnection, the client sends both the session ID and the last offset it has processed, and the server tries to restore the state
+
+The in-memory adapter already supports this feature, and we will soon update the Postgres and MongoDB adapters. We will also create a new adapter based on [Redis Streams](https://redis.io/docs/data-types/streams/), which will support this feature.
+
+Added in [54d5ee0](https://github.com/socketio/socket.io/commit/54d5ee05a684371191e207b8089f09fc24eb5107).
+
+#### Compatibility (for real) with Express middlewares
+
+This feature implements middlewares at the Engine.IO level, because Socket.IO middlewares are meant for namespace authorization and are not executed during a classic HTTP request/response cycle.
+
+Syntax:
+
+```js
+io.engine.use((req, res, next) => {
+  // do something
+
+  next();
+});
+
+// with express-session
+import session from "express-session";
+
+io.engine.use(session({
+  secret: "keyboard cat",
+  resave: false,
+  saveUninitialized: true,
+  cookie: { secure: true }
+}));
+
+// with helmet
+import helmet from "helmet";
+
+io.engine.use(helmet());
+```
+
+A workaround was possible by using the allowRequest option and the "headers" event, but this feels way cleaner and works with upgrade requests too.
+
+Added in [24786e7](https://github.com/socketio/engine.io/commit/24786e77c5403b1c4b5a2bc84e2af06f9187f74a).
+
+#### Error details in the disconnecting and disconnect events
+
+The `disconnect` event will now contain additional details about the disconnection reason.
+
+```js
+io.on("connection", (socket) => {
+  socket.on("disconnect", (reason, description) => {
+    console.log(description);
+  });
+});
+```
+
+Added in [8aa9499](https://github.com/socketio/socket.io/commit/8aa94991cee5518567d6254eec04b23f81510257).
+
+#### Automatic removal of empty child namespaces
+
+This commit adds a new option, "cleanupEmptyChildNamespaces". With this option enabled (disabled by default), when a socket disconnects from a dynamic namespace and if there are no other sockets connected to it then the namespace will be cleaned up and its adapter will be closed. 
+
+```js
+import { createServer } from "node:http";
+import { Server } from "socket.io";
+
+const httpServer = createServer();
+const io = new Server(httpServer, {
+  cleanupEmptyChildNamespaces: true
+});
+```
+
+Added in [5d9220b](https://github.com/socketio/socket.io/commit/5d9220b69adf73e086c27bbb63a4976b348f7c4c).
+
+#### A new "addTrailingSlash" option
+
+The trailing slash which was added by default can now be disabled:
+
+```js
+import { createServer } from "node:http";
+import { Server } from "socket.io";
+
+const httpServer = createServer();
+const io = new Server(httpServer, {
+  addTrailingSlash: false
+});
+```
+
+In the example above, the clients can omit the trailing slash and use `/socket.io` instead of `/socket.io/`.
+
+Added in [d0fd474](https://github.com/socketio/engine.io/commit/d0fd4746afa396297f07bb62e539b0c1c4018d7c).
+
+### Performance Improvements
+
+* precompute the WebSocket frames when broadcasting ([da2b542](https://github.com/socketio/socket.io/commit/da2b54279749adc5279c9ac4742b01b36c01cff0))
+
+
+### Dependencies
+
+- [`engine.io@~6.4.0`](https://github.com/socketio/engine.io/releases/tag/6.4.0) ([diff](https://github.com/socketio/engine.io/compare/6.2.0...6.2.1))
+- [`ws@~8.11.0`](https://github.com/websockets/ws/releases/tag/8.11.0) ([diff](https://github.com/websockets/ws/compare/8.2.3...8.11.0))
+
+
+## [4.5.4](https://github.com/socketio/socket.io/compare/4.5.3...4.5.4) (2022-11-22)
+
+This release contains a bump of:
+
+- `engine.io` in order to fix [CVE-2022-41940](https://github.com/socketio/engine.io/security/advisories/GHSA-r7qp-cfhv-p84w)
+- `socket.io-parser` in order to fix [CVE-2022-2421](https://github.com/advisories/GHSA-qm95-pgcg-qqfq).
+
+### Dependencies
+
+- [`engine.io@~6.2.1`](https://github.com/socketio/engine.io/releases/tag/6.2.1) ([diff](https://github.com/socketio/engine.io/compare/6.2.0...6.2.1))
+- [`ws@~8.2.3`](https://github.com/websockets/ws/releases/tag/8.2.3) (no change)
+
+
+
+## [4.5.3](https://github.com/socketio/socket.io/compare/4.5.2...4.5.3) (2022-10-15)
+
+
+### Bug Fixes
+
+* **typings:** accept an HTTP2 server in the constructor ([d3d0a2d](https://github.com/socketio/socket.io/commit/d3d0a2d5beaff51fd145f810bcaf6914213f8a06))
+* **typings:** apply types to "io.timeout(...).emit()" calls ([e357daf](https://github.com/socketio/socket.io/commit/e357daf5858560bc84e7e50cd36f0278d6721ea1))
+
+
+
+## [4.5.2](https://github.com/socketio/socket.io/compare/4.5.1...4.5.2) (2022-09-02)
+
+
+### Bug Fixes
+
+* prevent the socket from joining a room after disconnection ([18f3fda](https://github.com/socketio/socket.io/commit/18f3fdab12947a9fee3e9c37cfc1da97027d1473))
+* **uws:** prevent the server from crashing after upgrade ([ba497ee](https://github.com/socketio/socket.io/commit/ba497ee3eb52c4abf1464380d015d8c788714364))
+
+
+
+# [2.5.0](https://github.com/socketio/socket.io/compare/2.4.1...2.5.0) (2022-06-26)
+
+⚠️ WARNING ⚠️
+
+The default value of the maxHttpBufferSize option has been decreased from 100 MB to 1 MB, in order to prevent attacks by denial of service.
+
+Security advisory: [GHSA-j4f2-536g-r55m](https://github.com/advisories/GHSA-j4f2-536g-r55m)
+
+
+### Bug Fixes
+
+* fix race condition in dynamic namespaces ([05e1278](https://github.com/socketio/socket.io/commit/05e1278cfa99f3ecf3f8f0531ffe57d850e9a05b))
+* ignore packet received after disconnection ([22d4bdf](https://github.com/socketio/socket.io/commit/22d4bdf00d1a03885dc0171125faddfaef730066))
+* only set 'connected' to true after middleware execution ([226cc16](https://github.com/socketio/socket.io/commit/226cc16165f9fe60f16ff4d295fb91c8971cde35))
+* prevent the socket from joining a room after disconnection ([f223178](https://github.com/socketio/socket.io/commit/f223178eb655a7713303b21a78f9ef9e161d6458))
+
+
+
 ## [4.5.1](https://github.com/socketio/socket.io/compare/4.5.0...4.5.1) (2022-05-17)
 
 
@@ -234,6 +542,16 @@ we only add a field in the JSON-encoded handshake data:
 * allow integers as event names ([1c220dd](https://github.com/socketio/socket.io-parser/commit/1c220ddbf45ea4b44bc8dbf6f9ae245f672ba1b9))
 
 
+
+## [2.4.1](https://github.com/socketio/socket.io/compare/2.4.0...2.4.1) (2021-01-07)
+
+
+### Reverts
+
+* fix(security): do not allow all origins by default ([a169050](https://github.com/socketio/socket.io/commit/a1690509470e9dd5559cec4e60908ca6c23e9ba0))
+
+
+
 ## [3.0.5](https://github.com/socketio/socket.io/compare/3.0.4...3.0.5) (2021-01-05)
 
 
@@ -247,6 +565,17 @@ we only add a field in the JSON-encoded handshake data:
 * restore the socket middleware functionality ([bf54327](https://github.com/socketio/socket.io/commit/bf5432742158e4d5ba2722cff4a614967dffa5b9))
 
 
+
+# [2.4.0](https://github.com/socketio/socket.io/compare/2.3.0...2.4.0) (2021-01-04)
+
+
+### Bug Fixes
+
+* **security:** do not allow all origins by default ([f78a575](https://github.com/socketio/socket.io/commit/f78a575f66ab693c3ea96ea88429ddb1a44c86c7))
+* properly overwrite the query sent in the handshake ([d33a619](https://github.com/socketio/socket.io/commit/d33a619905a4905c153d4fec337c74da5b533a9e))
+
+
+
 ## [3.0.4](https://github.com/socketio/socket.io/compare/3.0.3...3.0.4) (2020-12-07)
 
 
@@ -532,3 +861,78 @@ io.of("/admin").use((socket, next) => {
 
 This method was kept for backward-compatibility with pre-1.0 versions.
 
+
+
+# [2.3.0](https://github.com/socketio/socket.io/compare/2.2.0...2.3.0) (2019-09-20)
+
+This release mainly contains a bump of the `engine.io` and `ws` packages, but no additional features.
+
+
+
+# [2.2.0](https://github.com/socketio/socket.io/compare/2.1.1...2.2.0) (2018-11-29)
+
+### Features
+
+- add cache-control header when serving the client source ([#2907](https://github.com/socketio/socket.io/pull/2907)) ([b00ae50](https://github.com/socketio/socket.io/commit/b00ae50be65d1bc88fa95145f1c486a6886a6b76))
+
+### Bug fixes
+
+- throw an error when trying to access the clients of a dynamic namespace ([#3355](https://github.com/socketio/socket.io/pull/3355)) ([a7fbd1a](https://github.com/socketio/socket.io/commit/a7fbd1ac4a47cafd832fc62e371754df924c5903))
+
+
+
+# [2.1.1](https://github.com/socketio/socket.io/compare/2.1.0...2.1.1) (2018-05-17)
+
+### Features
+
+- add local flag to the socket object ([#3129](https://github.com/socketio/socket.io/pull/3219)) ([1decae3](https://github.com/socketio/socket.io/commit/1decae341c80c0417b32d3124ca30c005240b48a))
+
+```js
+socket.local.to('room101').emit(/* */);
+```
+
+
+# [2.1.0](https://github.com/socketio/socket.io/compare/2.1.1...2.2.0) (2018-03-29)
+
+### Features
+
+- add a 'binary' flag ([#3185](https://github.com/socketio/socket.io/pull/3185)) ([f48a06c](https://github.com/socketio/socket.io/commit/f48a06c040280b44f90fd225c888910544fd63b5))
+
+```js
+// by default, the object is recursively scanned to check whether it contains some binary data
+// in the following example, the check is skipped in order to improve performance
+socket.binary(false).emit('plain-object', object);
+
+// it also works at the namespace level
+io.binary(false).emit('plain-object', object);
+```
+
+- add support for dynamic namespaces ([#3195](https://github.com/socketio/socket.io/pull/3195)) ([c0c79f0](https://github.com/socketio/socket.io/commit/c0c79f019e7138194e438339f8192705957c8ec3))
+
+```js
+io.of(/^\/dynamic-\d+$/).on('connect', (socket) => {
+  // socket.nsp.name = '/dynamic-101'
+});
+
+// client-side
+const client = require('socket.io-client')('/dynamic-101');
+```
+
+### Bug fixes
+
+- properly emit 'connect' when using a custom namespace ([#3197](https://github.com/socketio/socket.io/pull/3197)) ([f4fc517](https://github.com/socketio/socket.io/commit/f4fc517e0fe25866c95b584291487b8cbdff889d))
+- include the protocol in the origins check ([#3198](https://github.com/socketio/socket.io/pull/3198)) ([1f1d64b](https://github.com/socketio/socket.io/commit/1f1d64bab61a273712a199591a3f76210d8c0959))
+
+### Important note :warning: from Engine.IO [3.2.0 release](https://github.com/socketio/engine.io/releases/tag/3.2.0)
+
+There are two non-breaking changes that are somehow quite important:
+
+- `ws` was reverted as the default wsEngine (https://github.com/socketio/engine.io/pull/550), as there was several blocking issues with `uws`. You can still use `uws` by running `npm install uws --save` in your project and using the `wsEngine` option:
+```js
+var engine = require('engine.io');
+var server = engine.listen(3000, {
+  wsEngine: 'uws'
+});
+```
+
+- `pingTimeout` now defaults to 5 seconds (instead of 60 seconds): https://github.com/socketio/engine.io/pull/551

Readme.md

@@ -21,6 +21,7 @@ Some implementations in other languages are also available:
 - [Dart](https://github.com/rikulo/socket.io-client-dart)
 - [Python](https://github.com/miguelgrinberg/python-socketio)
 - [.NET](https://github.com/doghappy/socket.io-client-csharp)
+- [Rust](https://github.com/1c3t3a/rust-socketio)
 
 Its main features are:
 
@@ -125,7 +126,7 @@ io.listen(3000);
 
 Starting with **3.0**, express applications have become request handler
 functions that you pass to `http` or `http` `Server` instances. You need
-to pass the `Server` to `socket.io`, and not the express application
+to pass the `Server` to `socket.io`, not the express application
 function. Also make sure to call `.listen` on the `server`, not the `app`.
 
 ```js

SECURITY.md

@@ -0,0 +1,22 @@
+# Security Policy
+
+## Supported Versions
+
+| Version | Supported          |
+|---------|--------------------|
+| 4.x     | :white_check_mark: |
+| 3.x     | :white_check_mark: |
+| 2.4.x   | :white_check_mark: |
+| < 2.4.0 | :x:                |
+
+## Reporting a Vulnerability
+
+To report a security vulnerability in this package, please send an email to [@darrachequesne](https://github.com/darrachequesne) (see address in profile) describing the vulnerability and how to reproduce it.
+
+We will get back to you as soon as possible and publish a fix if necessary.
+
+:warning: IMPORTANT :warning: please do not create an issue in this repository, as attackers might take advantage of it. Thank you in advance for your responsible disclosure.
+
+## History
+
+No security vulnerability were reported yet.

examples/basic-crud-application/server/package.json

@@ -24,14 +24,14 @@
     "uuid": "^8.3.2"
   },
   "devDependencies": {
-    "@types/mocha": "^8.2.3",
     "@types/chai": "^4.2.16",
+    "@types/mocha": "^10.0.0",
     "@types/uuid": "^8.3.0",
     "chai": "^4.3.4",
-    "mocha": "^8.3.2",
+    "mocha": "^10.0.0",
     "nyc": "^15.1.0",
     "socket.io-client": "^4.0.1",
-    "ts-node": "^9.1.1",
+    "ts-node": "^10.9.1",
     "typescript": "^4.2.4"
   }
 }

lib/broadcast-operator.ts

@@ -7,6 +7,11 @@ import type {
   EventNames,
   EventsMap,
   TypedEventBroadcaster,
+  DecorateAcknowledgements,
+  DecorateAcknowledgementsWithTimeoutAndMultipleResponses,
+  AllButLast,
+  Last,
+  SecondArg,
 } from "./typed-events";
 
 export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
@@ -16,24 +21,35 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
     private readonly adapter: Adapter,
     private readonly rooms: Set<Room> = new Set<Room>(),
     private readonly exceptRooms: Set<Room> = new Set<Room>(),
-    private readonly flags: BroadcastFlags = {}
+    private readonly flags: BroadcastFlags & {
+      expectSingleResponse?: boolean;
+    } = {}
   ) {}
 
   /**
    * Targets a room when emitting.
    *
-   * @param room
-   * @return a new BroadcastOperator instance
-   * @public
+   * @example
+   * // the “foo” event will be broadcast to all connected clients in the “room-101” room
+   * io.to("room-101").emit("foo", "bar");
+   *
+   * // with an array of rooms (a client will be notified at most once)
+   * io.to(["room-101", "room-102"]).emit("foo", "bar");
+   *
+   * // with multiple chained calls
+   * io.to("room-101").to("room-102").emit("foo", "bar");
+   *
+   * @param room - a room, or an array of rooms
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public to(room: Room | Room[]): BroadcastOperator<EmitEvents, SocketData> {
+  public to(room: Room | Room[]) {
     const rooms = new Set(this.rooms);
     if (Array.isArray(room)) {
       room.forEach((r) => rooms.add(r));
     } else {
       rooms.add(room);
     }
-    return new BroadcastOperator(
+    return new BroadcastOperator<EmitEvents, SocketData>(
       this.adapter,
       rooms,
       this.exceptRooms,
@@ -42,33 +58,43 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
   }
 
   /**
-   * Targets a room when emitting.
+   * Targets a room when emitting. Similar to `to()`, but might feel clearer in some cases:
    *
-   * @param room
-   * @return a new BroadcastOperator instance
-   * @public
+   * @example
+   * // disconnect all clients in the "room-101" room
+   * io.in("room-101").disconnectSockets();
+   *
+   * @param room - a room, or an array of rooms
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public in(room: Room | Room[]): BroadcastOperator<EmitEvents, SocketData> {
+  public in(room: Room | Room[]) {
     return this.to(room);
   }
 
   /**
    * Excludes a room when emitting.
    *
-   * @param room
-   * @return a new BroadcastOperator instance
-   * @public
+   * @example
+   * // the "foo" event will be broadcast to all connected clients, except the ones that are in the "room-101" room
+   * io.except("room-101").emit("foo", "bar");
+   *
+   * // with an array of rooms
+   * io.except(["room-101", "room-102"]).emit("foo", "bar");
+   *
+   * // with multiple chained calls
+   * io.except("room-101").except("room-102").emit("foo", "bar");
+   *
+   * @param room - a room, or an array of rooms
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public except(
-    room: Room | Room[]
-  ): BroadcastOperator<EmitEvents, SocketData> {
+  public except(room: Room | Room[]) {
     const exceptRooms = new Set(this.exceptRooms);
     if (Array.isArray(room)) {
       room.forEach((r) => exceptRooms.add(r));
     } else {
       exceptRooms.add(room);
     }
-    return new BroadcastOperator(
+    return new BroadcastOperator<EmitEvents, SocketData>(
       this.adapter,
       this.rooms,
       exceptRooms,
@@ -79,15 +105,15 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
   /**
    * Sets the compress flag.
    *
+   * @example
+   * io.compress(false).emit("hello");
+   *
    * @param compress - if `true`, compresses the sending data
    * @return a new BroadcastOperator instance
-   * @public
    */
-  public compress(
-    compress: boolean
-  ): BroadcastOperator<EmitEvents, SocketData> {
+  public compress(compress: boolean) {
     const flags = Object.assign({}, this.flags, { compress });
-    return new BroadcastOperator(
+    return new BroadcastOperator<EmitEvents, SocketData>(
       this.adapter,
       this.rooms,
       this.exceptRooms,
@@ -100,12 +126,14 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
    * receive messages (because of network slowness or other issues, or because they’re connected through long polling
    * and is in the middle of a request-response cycle).
    *
+   * @example
+   * io.volatile.emit("hello"); // the clients may or may not receive it
+   *
    * @return a new BroadcastOperator instance
-   * @public
    */
-  public get volatile(): BroadcastOperator<EmitEvents, SocketData> {
+  public get volatile() {
     const flags = Object.assign({}, this.flags, { volatile: true });
-    return new BroadcastOperator(
+    return new BroadcastOperator<EmitEvents, SocketData>(
       this.adapter,
       this.rooms,
       this.exceptRooms,
@@ -116,12 +144,15 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
   /**
    * Sets a modifier for a subsequent event emission that the event data will only be broadcast to the current node.
    *
-   * @return a new BroadcastOperator instance
-   * @public
+   * @example
+   * // the “foo” event will be broadcast to all connected clients on this node
+   * io.local.emit("foo", "bar");
+   *
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public get local(): BroadcastOperator<EmitEvents, SocketData> {
+  public get local() {
     const flags = Object.assign({}, this.flags, { local: true });
-    return new BroadcastOperator(
+    return new BroadcastOperator<EmitEvents, SocketData>(
       this.adapter,
       this.rooms,
       this.exceptRooms,
@@ -132,38 +163,52 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
   /**
    * Adds a timeout in milliseconds for the next operation
    *
-   * <pre><code>
-   *
+   * @example
    * io.timeout(1000).emit("some-event", (err, responses) => {
-   *   // ...
+   *   if (err) {
+   *     // some clients did not acknowledge the event in the given delay
+   *   } else {
+   *     console.log(responses); // one response per client
+   *   }
    * });
    *
-   * </pre></code>
-   *
    * @param timeout
    */
   public timeout(timeout: number) {
     const flags = Object.assign({}, this.flags, { timeout });
-    return new BroadcastOperator(
-      this.adapter,
-      this.rooms,
-      this.exceptRooms,
-      flags
-    );
+    return new BroadcastOperator<
+      DecorateAcknowledgementsWithTimeoutAndMultipleResponses<EmitEvents>,
+      SocketData
+    >(this.adapter, this.rooms, this.exceptRooms, flags);
   }
 
   /**
    * Emits to all clients.
    *
+   * @example
+   * // the “foo” event will be broadcast to all connected clients
+   * io.emit("foo", "bar");
+   *
+   * // the “foo” event will be broadcast to all connected clients in the “room-101” room
+   * io.to("room-101").emit("foo", "bar");
+   *
+   * // with an acknowledgement expected from all connected clients
+   * io.timeout(1000).emit("some-event", (err, responses) => {
+   *   if (err) {
+   *     // some clients did not acknowledge the event in the given delay
+   *   } else {
+   *     console.log(responses); // one response per client
+   *   }
+   * });
+   *
    * @return Always true
-   * @public
    */
   public emit<Ev extends EventNames<EmitEvents>>(
     ev: Ev,
     ...args: EventParams<EmitEvents, Ev>
   ): boolean {
     if (RESERVED_EVENTS.has(ev)) {
-      throw new Error(`"${ev}" is a reserved event name`);
+      throw new Error(`"${String(ev)}" is a reserved event name`);
     }
     // set up packet object
     const data = [ev, ...args];
@@ -190,7 +235,10 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
 
     const timer = setTimeout(() => {
       timedOut = true;
-      ack.apply(this, [new Error("operation has timed out"), responses]);
+      ack.apply(this, [
+        new Error("operation has timed out"),
+        this.flags.expectSingleResponse ? null : responses,
+      ]);
     }, this.flags.timeout);
 
     let expectedServerCount = -1;
@@ -204,7 +252,10 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
         responses.length === expectedClientCount
       ) {
         clearTimeout(timer);
-        ack.apply(this, [null, responses]);
+        ack.apply(this, [
+          null,
+          this.flags.expectSingleResponse ? null : responses,
+        ]);
       }
     };
 
@@ -236,10 +287,41 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
     return true;
   }
 
+  /**
+   * Emits an event and waits for an acknowledgement from all clients.
+   *
+   * @example
+   * try {
+   *   const responses = await io.timeout(1000).emitWithAck("some-event");
+   *   console.log(responses); // one response per client
+   * } catch (e) {
+   *   // some clients did not acknowledge the event in the given delay
+   * }
+   *
+   * @return a Promise that will be fulfilled when all clients have acknowledged the event
+   */
+  public emitWithAck<Ev extends EventNames<EmitEvents>>(
+    ev: Ev,
+    ...args: AllButLast<EventParams<EmitEvents, Ev>>
+  ): Promise<SecondArg<Last<EventParams<EmitEvents, Ev>>>> {
+    return new Promise((resolve, reject) => {
+      args.push((err, responses) => {
+        if (err) {
+          err.responses = responses;
+          return reject(err);
+        } else {
+          return resolve(responses);
+        }
+      });
+      this.emit(ev, ...(args as any[] as EventParams<EmitEvents, Ev>));
+    });
+  }
+
   /**
    * Gets a list of clients.
    *
-   * @public
+   * @deprecated this method will be removed in the next major release, please use {@link Server#serverSideEmit} or
+   * {@link fetchSockets} instead.
    */
   public allSockets(): Promise<Set<SocketId>> {
     if (!this.adapter) {
@@ -251,13 +333,30 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
   }
 
   /**
-   * Returns the matching socket instances
+   * Returns the matching socket instances. This method works across a cluster of several Socket.IO servers.
    *
-   * @public
+   * Note: this method also works within a cluster of multiple Socket.IO servers, with a compatible {@link Adapter}.
+   *
+   * @example
+   * // return all Socket instances
+   * const sockets = await io.fetchSockets();
+   *
+   * // return all Socket instances in the "room1" room
+   * const sockets = await io.in("room1").fetchSockets();
+   *
+   * for (const socket of sockets) {
+   *   console.log(socket.id);
+   *   console.log(socket.handshake);
+   *   console.log(socket.rooms);
+   *   console.log(socket.data);
+   *
+   *   socket.emit("hello");
+   *   socket.join("room1");
+   *   socket.leave("room2");
+   *   socket.disconnect();
+   * }
    */
-  public fetchSockets<SocketData = any>(): Promise<
-    RemoteSocket<EmitEvents, SocketData>[]
-  > {
+  public fetchSockets(): Promise<RemoteSocket<EmitEvents, SocketData>[]> {
     return this.adapter
       .fetchSockets({
         rooms: this.rooms,
@@ -280,10 +379,19 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
   }
 
   /**
-   * Makes the matching socket instances join the specified rooms
+   * Makes the matching socket instances join the specified rooms.
    *
-   * @param room
-   * @public
+   * Note: this method also works within a cluster of multiple Socket.IO servers, with a compatible {@link Adapter}.
+   *
+   * @example
+   *
+   * // make all socket instances join the "room1" room
+   * io.socketsJoin("room1");
+   *
+   * // make all socket instances in the "room1" room join the "room2" and "room3" rooms
+   * io.in("room1").socketsJoin(["room2", "room3"]);
+   *
+   * @param room - a room, or an array of rooms
    */
   public socketsJoin(room: Room | Room[]): void {
     this.adapter.addSockets(
@@ -297,10 +405,18 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
   }
 
   /**
-   * Makes the matching socket instances leave the specified rooms
+   * Makes the matching socket instances leave the specified rooms.
    *
-   * @param room
-   * @public
+   * Note: this method also works within a cluster of multiple Socket.IO servers, with a compatible {@link Adapter}.
+   *
+   * @example
+   * // make all socket instances leave the "room1" room
+   * io.socketsLeave("room1");
+   *
+   * // make all socket instances in the "room1" room leave the "room2" and "room3" rooms
+   * io.in("room1").socketsLeave(["room2", "room3"]);
+   *
+   * @param room - a room, or an array of rooms
    */
   public socketsLeave(room: Room | Room[]): void {
     this.adapter.delSockets(
@@ -314,10 +430,18 @@ export class BroadcastOperator<EmitEvents extends EventsMap, SocketData>
   }
 
   /**
-   * Makes the matching socket instances disconnect
+   * Makes the matching socket instances disconnect.
+   *
+   * Note: this method also works within a cluster of multiple Socket.IO servers, with a compatible {@link Adapter}.
+   *
+   * @example
+   * // make all socket instances disconnect (the connections might be kept alive for other namespaces)
+   * io.disconnectSockets();
+   *
+   * // make all socket instances in the "room1" room disconnect and close the underlying connections
+   * io.in("room1").disconnectSockets(true);
    *
    * @param close - whether to close the underlying connection
-   * @public
    */
   public disconnectSockets(close: boolean = false): void {
     this.adapter.disconnectSockets(
@@ -359,7 +483,44 @@ export class RemoteSocket<EmitEvents extends EventsMap, SocketData>
     this.handshake = details.handshake;
     this.rooms = new Set(details.rooms);
     this.data = details.data;
-    this.operator = new BroadcastOperator(adapter, new Set([this.id]));
+    this.operator = new BroadcastOperator<EmitEvents, SocketData>(
+      adapter,
+      new Set([this.id]),
+      new Set(),
+      {
+        expectSingleResponse: true, // so that remoteSocket.emit() with acknowledgement behaves like socket.emit()
+      }
+    );
+  }
+
+  /**
+   * Adds a timeout in milliseconds for the next operation.
+   *
+   * @example
+   * const sockets = await io.fetchSockets();
+   *
+   * for (const socket of sockets) {
+   *   if (someCondition) {
+   *     socket.timeout(1000).emit("some-event", (err) => {
+   *       if (err) {
+   *         // the client did not acknowledge the event in the given delay
+   *       }
+   *     });
+   *   }
+   * }
+   *
+   * // note: if possible, using a room instead of looping over all sockets is preferable
+   * io.timeout(1000).to(someConditionRoom).emit("some-event", (err, responses) => {
+   *   // ...
+   * });
+   *
+   * @param timeout
+   */
+  public timeout(timeout: number) {
+    return this.operator.timeout(timeout) as BroadcastOperator<
+      DecorateAcknowledgements<EmitEvents>,
+      SocketData
+    >;
   }
 
   public emit<Ev extends EventNames<EmitEvents>>(
@@ -373,7 +534,6 @@ export class RemoteSocket<EmitEvents extends EventsMap, SocketData>
    * Joins a room.
    *
    * @param {String|Array} room - room or array of rooms
-   * @public
    */
   public join(room: Room | Room[]): void {
     return this.operator.socketsJoin(room);
@@ -383,7 +543,6 @@ export class RemoteSocket<EmitEvents extends EventsMap, SocketData>
    * Leaves a room.
    *
    * @param {String} room
-   * @public
    */
   public leave(room: Room): void {
     return this.operator.socketsLeave(room);
@@ -394,8 +553,6 @@ export class RemoteSocket<EmitEvents extends EventsMap, SocketData>
    *
    * @param {Boolean} close - if `true`, closes the underlying connection
    * @return {Socket} self
-   *
-   * @public
    */
   public disconnect(close = false): this {
     this.operator.disconnectSockets(close);

lib/client.ts

@@ -18,6 +18,13 @@ interface WriteOptions {
   wsPreEncoded?: string;
 }
 
+type CloseReason =
+  | "transport error"
+  | "transport close"
+  | "forced close"
+  | "ping timeout"
+  | "parse error";
+
 export class Client<
   ListenEvents extends EventsMap,
   EmitEvents extends EventsMap,
@@ -107,7 +114,7 @@ export class Client<
    * @param {Object} auth - the auth parameters
    * @private
    */
-  private connect(name: string, auth: object = {}): void {
+  private connect(name: string, auth: Record<string, unknown> = {}): void {
     if (this.server._nsps.has(name)) {
       debug("connecting to namespace %s", name);
       return this.doConnect(name, auth);
@@ -145,10 +152,10 @@ export class Client<
    *
    * @private
    */
-  private doConnect(name: string, auth: object): void {
+  private doConnect(name: string, auth: Record<string, unknown>): void {
     const nsp = this.server.of(name);
 
-    const socket = nsp._add(this, auth, () => {
+    nsp._add(this, auth, (socket) => {
       this.sockets.set(socket.id, socket);
       this.nsps.set(nsp.name, socket);
 
@@ -221,7 +228,7 @@ export class Client<
   }
 
   private writeToEngine(
-    encodedPackets: Array<String | Buffer>,
+    encodedPackets: Array<string | Buffer>,
     opts: WriteOptions
   ): void {
     if (opts.volatile && !this.conn.transport.writable) {
@@ -260,7 +267,7 @@ export class Client<
    */
   private ondecoded(packet: Packet): void {
     let namespace: string;
-    let authPayload;
+    let authPayload: Record<string, unknown>;
     if (this.conn.protocol === 3) {
       const parsed = url.parse(packet.nsp, true);
       namespace = parsed.pathname!;
@@ -304,9 +311,13 @@ export class Client<
    * Called upon transport close.
    *
    * @param reason
+   * @param description
    * @private
    */
-  private onclose(reason: string): void {
+  private onclose(
+    reason: CloseReason | "forced server close",
+    description?: any
+  ): void {
     debug("client close with reason %s", reason);
 
     // ignore a potential subsequent `close` event
@@ -314,7 +325,7 @@ export class Client<
 
     // `nsps` and `sockets` are cleaned up seamlessly
     for (const socket of this.sockets.values()) {
-      socket._onclose(reason);
+      socket._onclose(reason, description);
     }
     this.sockets.clear();
 

lib/index.ts

@@ -1,26 +1,31 @@
 import http = require("http");
 import type { Server as HTTPSServer } from "https";
+import type { Http2SecureServer } from "http2";
 import { createReadStream } from "fs";
 import { createDeflate, createGzip, createBrotliCompress } from "zlib";
 import accepts = require("accepts");
 import { pipeline } from "stream";
 import path = require("path");
-import {
-  attach,
-  Server as Engine,
+import { attach, Server as Engine, uServer } from "engine.io";
+import type {
   ServerOptions as EngineOptions,
   AttachOptions,
-  uServer,
+  BaseServer,
 } from "engine.io";
 import { Client } from "./client";
 import { EventEmitter } from "events";
 import { ExtendedError, Namespace, ServerReservedEventsMap } from "./namespace";
 import { ParentNamespace } from "./parent-namespace";
-import { Adapter, Room, SocketId } from "socket.io-adapter";
+import {
+  Adapter,
+  SessionAwareAdapter,
+  Room,
+  SocketId,
+} from "socket.io-adapter";
 import * as parser from "socket.io-parser";
 import type { Encoder } from "socket.io-parser";
 import debugModule from "debug";
-import { Socket } from "./socket";
+import { Socket, DisconnectReason } from "./socket";
 import type { BroadcastOperator, RemoteSocket } from "./broadcast-operator";
 import {
   EventsMap,
@@ -28,6 +33,11 @@ import {
   EventParams,
   StrictEventEmitter,
   EventNames,
+  DecorateAcknowledgementsWithTimeoutAndMultipleResponses,
+  AllButLast,
+  Last,
+  FirstArg,
+  SecondArg,
 } from "./typed-events";
 import { patchAdapter, restoreAdapter, serveFile } from "./uws";
 
@@ -70,8 +80,58 @@ interface ServerOptions extends EngineOptions, AttachOptions {
    * @default 45000
    */
   connectTimeout: number;
+  /**
+   * Whether to enable the recovery of connection state when a client temporarily disconnects.
+   *
+   * The connection state includes the missed packets, the rooms the socket was in and the `data` attribute.
+   */
+  connectionStateRecovery: {
+    /**
+     * The backup duration of the sessions and the packets.
+     *
+     * @default 120000 (2 minutes)
+     */
+    maxDisconnectionDuration?: number;
+    /**
+     * Whether to skip middlewares upon successful connection state recovery.
+     *
+     * @default true
+     */
+    skipMiddlewares?: boolean;
+  };
+  /**
+   * Whether to remove child namespaces that have no sockets connected to them
+   * @default false
+   */
+  cleanupEmptyChildNamespaces: boolean;
 }
 
+/**
+ * Represents a Socket.IO server.
+ *
+ * @example
+ * import { Server } from "socket.io";
+ *
+ * const io = new Server();
+ *
+ * io.on("connection", (socket) => {
+ *   console.log(`socket ${socket.id} connected`);
+ *
+ *   // send an event to the client
+ *   socket.emit("foo", "bar");
+ *
+ *   socket.on("foobar", () => {
+ *     // an event was received from the client
+ *   });
+ *
+ *   // upon disconnection
+ *   socket.on("disconnect", (reason) => {
+ *     console.log(`socket ${socket.id} disconnected due to ${reason}`);
+ *   });
+ * });
+ *
+ * io.listen(3000);
+ */
 export class Server<
   ListenEvents extends EventsMap = DefaultEventsMap,
   EmitEvents extends EventsMap = ListenEvents,
@@ -96,14 +156,11 @@ export class Server<
   /**
    * A reference to the underlying Engine.IO server.
    *
-   * Example:
-   *
-   * <code>
-   *   const clientsCount = io.engine.clientsCount;
-   * </code>
+   * @example
+   * const clientsCount = io.engine.clientsCount;
    *
    */
-  public engine: any;
+  public engine: BaseServer;
 
   /** @private */
   readonly _parser: typeof parser;
@@ -121,9 +178,21 @@ export class Server<
     ParentNspNameMatchFn,
     ParentNamespace<ListenEvents, EmitEvents, ServerSideEvents, SocketData>
   > = new Map();
+
+  /**
+   * A subset of the {@link parentNsps} map, only containing {@link ParentNamespace} which are based on a regular
+   * expression.
+   *
+   * @private
+   */
+  private parentNamespacesFromRegExp: Map<
+    RegExp,
+    ParentNamespace<ListenEvents, EmitEvents, ServerSideEvents, SocketData>
+  > = new Map();
+
   private _adapter?: AdapterConstructor;
   private _serveClient: boolean;
-  private opts: Partial<EngineOptions>;
+  private readonly opts: Partial<ServerOptions>;
   private eio: Engine;
   private _path: string;
   private clientPathRegex: RegExp;
@@ -132,18 +201,17 @@ export class Server<
    * @private
    */
   _connectTimeout: number;
-  private httpServer: http.Server | HTTPSServer;
+  private httpServer: http.Server | HTTPSServer | Http2SecureServer;
 
   /**
    * Server constructor.
    *
    * @param srv http server, port, or options
    * @param [opts]
-   * @public
    */
   constructor(opts?: Partial<ServerOptions>);
   constructor(
-    srv?: http.Server | HTTPSServer | number,
+    srv?: http.Server | HTTPSServer | Http2SecureServer | number,
     opts?: Partial<ServerOptions>
   );
   constructor(
@@ -152,6 +220,7 @@ export class Server<
       | Partial<ServerOptions>
       | http.Server
       | HTTPSServer
+      | Http2SecureServer
       | number,
     opts?: Partial<ServerOptions>
   );
@@ -161,6 +230,7 @@ export class Server<
       | Partial<ServerOptions>
       | http.Server
       | HTTPSServer
+      | Http2SecureServer
       | number,
     opts: Partial<ServerOptions> = {}
   ) {
@@ -178,11 +248,29 @@ export class Server<
     this.serveClient(false !== opts.serveClient);
     this._parser = opts.parser || parser;
     this.encoder = new this._parser.Encoder();
-    this.adapter(opts.adapter || Adapter);
-    this.sockets = this.of("/");
     this.opts = opts;
+    if (opts.connectionStateRecovery) {
+      opts.connectionStateRecovery = Object.assign(
+        {
+          maxDisconnectionDuration: 2 * 60 * 1000,
+          skipMiddlewares: true,
+        },
+        opts.connectionStateRecovery
+      );
+      this.adapter(opts.adapter || SessionAwareAdapter);
+    } else {
+      this.adapter(opts.adapter || Adapter);
+    }
+    opts.cleanupEmptyChildNamespaces = !!opts.cleanupEmptyChildNamespaces;
+    this.sockets = this.of("/");
     if (srv || typeof srv == "number")
-      this.attach(srv as http.Server | HTTPSServer | number);
+      this.attach(
+        srv as http.Server | HTTPSServer | Http2SecureServer | number
+      );
+  }
+
+  get _opts() {
+    return this.opts;
   }
 
   /**
@@ -190,7 +278,6 @@ export class Server<
    *
    * @param v - whether to serve client code
    * @return self when setting or value when getting
-   * @public
    */
   public serveClient(v: boolean): this;
   public serveClient(): boolean;
@@ -239,8 +326,6 @@ export class Server<
         }
         const namespace = this.parentNsps.get(nextFn.value)!.createChild(name);
         debug("dynamic namespace %s was created", name);
-        // @ts-ignore
-        this.sockets.emitReserved("new_namespace", namespace);
         fn(namespace);
       });
     };
@@ -253,7 +338,6 @@ export class Server<
    *
    * @param {String} v pathname
    * @return {Server|String} self when setting or value when getting
-   * @public
    */
   public path(v: string): this;
   public path(): string;
@@ -275,7 +359,6 @@ export class Server<
   /**
    * Set the delay after which a client without namespace is closed
    * @param v
-   * @public
    */
   public connectTimeout(v: number): this;
   public connectTimeout(): number;
@@ -291,7 +374,6 @@ export class Server<
    *
    * @param v pathname
    * @return self when setting or value when getting
-   * @public
    */
   public adapter(): AdapterConstructor | undefined;
   public adapter(v: AdapterConstructor): this;
@@ -312,10 +394,9 @@ export class Server<
    * @param srv - server or port
    * @param opts - options passed to engine.io
    * @return self
-   * @public
    */
   public listen(
-    srv: http.Server | HTTPSServer | number,
+    srv: http.Server | HTTPSServer | Http2SecureServer | number,
     opts: Partial<ServerOptions> = {}
   ): this {
     return this.attach(srv, opts);
@@ -327,10 +408,9 @@ export class Server<
    * @param srv - server or port
    * @param opts - options passed to engine.io
    * @return self
-   * @public
    */
   public attach(
-    srv: http.Server | HTTPSServer | number,
+    srv: http.Server | HTTPSServer | Http2SecureServer | number,
     opts: Partial<ServerOptions> = {}
   ): this {
     if ("function" == typeof srv) {
@@ -416,7 +496,7 @@ export class Server<
         res.writeHeader("cache-control", "public, max-age=0");
         res.writeHeader(
           "content-type",
-          "application/" + (isMap ? "json" : "javascript")
+          "application/" + (isMap ? "json" : "javascript") + "; charset=utf-8"
         );
         res.writeHeader("etag", expectedEtag);
 
@@ -436,7 +516,7 @@ export class Server<
    * @private
    */
   private initEngine(
-    srv: http.Server | HTTPSServer,
+    srv: http.Server | HTTPSServer | Http2SecureServer,
     opts: EngineOptions & AttachOptions
   ): void {
     // initialize engine
@@ -459,7 +539,9 @@ export class Server<
    * @param srv http server
    * @private
    */
-  private attachServe(srv: http.Server | HTTPSServer): void {
+  private attachServe(
+    srv: http.Server | HTTPSServer | Http2SecureServer
+  ): void {
     debug("attaching client serving req handler");
 
     const evs = srv.listeners("request").slice(0);
@@ -507,7 +589,7 @@ export class Server<
     res.setHeader("Cache-Control", "public, max-age=0");
     res.setHeader(
       "Content-Type",
-      "application/" + (isMap ? "json" : "javascript")
+      "application/" + (isMap ? "json" : "javascript") + "; charset=utf-8"
     );
     res.setHeader("ETag", expectedEtag);
 
@@ -559,11 +641,10 @@ export class Server<
   /**
    * Binds socket.io to an engine.io instance.
    *
-   * @param {engine.Server} engine engine.io (or compatible) server
+   * @param engine engine.io (or compatible) server
    * @return self
-   * @public
    */
-  public bind(engine): this {
+  public bind(engine: BaseServer): this {
     this.engine = engine;
     this.engine.on("connection", this.onconnection.bind(this));
     return this;
@@ -589,9 +670,20 @@ export class Server<
   /**
    * Looks up a namespace.
    *
-   * @param {String|RegExp|Function} name nsp name
+   * @example
+   * // with a simple string
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * // with a regex
+   * const dynamicNsp = io.of(/^\/dynamic-\d+$/).on("connection", (socket) => {
+   *   const namespace = socket.nsp; // newNamespace.name === "/dynamic-101"
+   *
+   *   // broadcast to all clients in the given sub-namespace
+   *   namespace.emit("hello");
+   * });
+   *
+   * @param name - nsp name
    * @param fn optional, nsp `connection` ev handler
-   * @public
    */
   public of(
     name: string | RegExp | ParentNspNameMatchFn,
@@ -609,6 +701,7 @@ export class Server<
           (nsp, conn, next) => next(null, (name as RegExp).test(nsp)),
           parentNsp
         );
+        this.parentNamespacesFromRegExp.set(name, parentNsp);
       }
       if (fn) {
         // @ts-ignore
@@ -621,6 +714,13 @@ export class Server<
 
     let nsp = this._nsps.get(name);
     if (!nsp) {
+      for (const [regex, parentNamespace] of this.parentNamespacesFromRegExp) {
+        if (regex.test(name as string)) {
+          debug("attaching namespace %s to parent namespace %s", name, regex);
+          return parentNamespace.createChild(name as string);
+        }
+      }
+
       debug("initializing namespace %s", name);
       nsp = new Namespace(this, name);
       this._nsps.set(name, nsp);
@@ -637,7 +737,6 @@ export class Server<
    * Closes server connection
    *
    * @param [fn] optional, called as `fn([err])` on error OR all conns closed
-   * @public
    */
   public close(fn?: (err?: Error) => void): void {
     for (const socket of this.sockets.sockets.values()) {
@@ -657,10 +756,15 @@ export class Server<
   }
 
   /**
-   * Sets up namespace middleware.
+   * Registers a middleware, which is a function that gets executed for every incoming {@link Socket}.
    *
-   * @return self
-   * @public
+   * @example
+   * io.use((socket, next) => {
+   *   // ...
+   *   next();
+   * });
+   *
+   * @param fn - the middleware function
    */
   public use(
     fn: (
@@ -675,43 +779,91 @@ export class Server<
   /**
    * Targets a room when emitting.
    *
-   * @param room
-   * @return self
-   * @public
+   * @example
+   * // the “foo” event will be broadcast to all connected clients in the “room-101” room
+   * io.to("room-101").emit("foo", "bar");
+   *
+   * // with an array of rooms (a client will be notified at most once)
+   * io.to(["room-101", "room-102"]).emit("foo", "bar");
+   *
+   * // with multiple chained calls
+   * io.to("room-101").to("room-102").emit("foo", "bar");
+   *
+   * @param room - a room, or an array of rooms
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public to(room: Room | Room[]): BroadcastOperator<EmitEvents, SocketData> {
+  public to(room: Room | Room[]) {
     return this.sockets.to(room);
   }
 
   /**
-   * Targets a room when emitting.
+   * Targets a room when emitting. Similar to `to()`, but might feel clearer in some cases:
    *
-   * @param room
-   * @return self
-   * @public
+   * @example
+   * // disconnect all clients in the "room-101" room
+   * io.in("room-101").disconnectSockets();
+   *
+   * @param room - a room, or an array of rooms
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public in(room: Room | Room[]): BroadcastOperator<EmitEvents, SocketData> {
+  public in(room: Room | Room[]) {
     return this.sockets.in(room);
   }
 
   /**
    * Excludes a room when emitting.
    *
-   * @param name
-   * @return self
-   * @public
+   * @example
+   * // the "foo" event will be broadcast to all connected clients, except the ones that are in the "room-101" room
+   * io.except("room-101").emit("foo", "bar");
+   *
+   * // with an array of rooms
+   * io.except(["room-101", "room-102"]).emit("foo", "bar");
+   *
+   * // with multiple chained calls
+   * io.except("room-101").except("room-102").emit("foo", "bar");
+   *
+   * @param room - a room, or an array of rooms
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public except(
-    name: Room | Room[]
-  ): BroadcastOperator<EmitEvents, SocketData> {
-    return this.sockets.except(name);
+  public except(room: Room | Room[]) {
+    return this.sockets.except(room);
+  }
+
+  /**
+   * Emits an event and waits for an acknowledgement from all clients.
+   *
+   * @example
+   * try {
+   *   const responses = await io.timeout(1000).emitWithAck("some-event");
+   *   console.log(responses); // one response per client
+   * } catch (e) {
+   *   // some clients did not acknowledge the event in the given delay
+   * }
+   *
+   * @return a Promise that will be fulfilled when all clients have acknowledged the event
+   */
+  public emitWithAck<Ev extends EventNames<EmitEvents>>(
+    ev: Ev,
+    ...args: AllButLast<EventParams<EmitEvents, Ev>>
+  ): Promise<SecondArg<Last<EventParams<EmitEvents, Ev>>>> {
+    return this.sockets.emitWithAck(ev, ...args);
   }
 
   /**
    * Sends a `message` event to all clients.
    *
+   * This method mimics the WebSocket.send() method.
+   *
+   * @see https://developer.mozilla.org/en-US/docs/Web/API/WebSocket/send
+   *
+   * @example
+   * io.send("hello");
+   *
+   * // this is equivalent to
+   * io.emit("message", "hello");
+   *
    * @return self
-   * @public
    */
   public send(...args: EventParams<EmitEvents, "message">): this {
     this.sockets.emit("message", ...args);
@@ -719,10 +871,9 @@ export class Server<
   }
 
   /**
-   * Sends a `message` event to all clients.
+   * Sends a `message` event to all clients. Alias of {@link send}.
    *
    * @return self
-   * @public
    */
   public write(...args: EventParams<EmitEvents, "message">): this {
     this.sockets.emit("message", ...args);
@@ -730,23 +881,69 @@ export class Server<
   }
 
   /**
-   * Emit a packet to other Socket.IO servers
+   * Sends a message to the other Socket.IO servers of the cluster.
+   *
+   * @example
+   * io.serverSideEmit("hello", "world");
+   *
+   * io.on("hello", (arg1) => {
+   *   console.log(arg1); // prints "world"
+   * });
+   *
+   * // acknowledgements (without binary content) are supported too:
+   * io.serverSideEmit("ping", (err, responses) => {
+   *  if (err) {
+   *     // some servers did not acknowledge the event in the given delay
+   *   } else {
+   *     console.log(responses); // one response per server (except the current one)
+   *   }
+   * });
+   *
+   * io.on("ping", (cb) => {
+   *   cb("pong");
+   * });
    *
    * @param ev - the event name
    * @param args - an array of arguments, which may include an acknowledgement callback at the end
-   * @public
    */
   public serverSideEmit<Ev extends EventNames<ServerSideEvents>>(
     ev: Ev,
-    ...args: EventParams<ServerSideEvents, Ev>
+    ...args: EventParams<
+      DecorateAcknowledgementsWithTimeoutAndMultipleResponses<ServerSideEvents>,
+      Ev
+    >
   ): boolean {
     return this.sockets.serverSideEmit(ev, ...args);
   }
 
+  /**
+   * Sends a message and expect an acknowledgement from the other Socket.IO servers of the cluster.
+   *
+   * @example
+   * try {
+   *   const responses = await io.serverSideEmitWithAck("ping");
+   *   console.log(responses); // one response per server (except the current one)
+   * } catch (e) {
+   *   // some servers did not acknowledge the event in the given delay
+   * }
+   *
+   * @param ev - the event name
+   * @param args - an array of arguments
+   *
+   * @return a Promise that will be fulfilled when all servers have acknowledged the event
+   */
+  public serverSideEmitWithAck<Ev extends EventNames<ServerSideEvents>>(
+    ev: Ev,
+    ...args: AllButLast<EventParams<ServerSideEvents, Ev>>
+  ): Promise<FirstArg<Last<EventParams<ServerSideEvents, Ev>>>[]> {
+    return this.sockets.serverSideEmitWithAck(ev, ...args);
+  }
+
   /**
    * Gets a list of socket ids.
    *
-   * @public
+   * @deprecated this method will be removed in the next major release, please use {@link Server#serverSideEmit} or
+   * {@link Server#fetchSockets} instead.
    */
   public allSockets(): Promise<Set<SocketId>> {
     return this.sockets.allSockets();
@@ -755,13 +952,13 @@ export class Server<
   /**
    * Sets the compress flag.
    *
+   * @example
+   * io.compress(false).emit("hello");
+   *
    * @param compress - if `true`, compresses the sending data
-   * @return self
-   * @public
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public compress(
-    compress: boolean
-  ): BroadcastOperator<EmitEvents, SocketData> {
+  public compress(compress: boolean) {
     return this.sockets.compress(compress);
   }
 
@@ -770,34 +967,40 @@ export class Server<
    * receive messages (because of network slowness or other issues, or because they’re connected through long polling
    * and is in the middle of a request-response cycle).
    *
-   * @return self
-   * @public
+   * @example
+   * io.volatile.emit("hello"); // the clients may or may not receive it
+   *
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public get volatile(): BroadcastOperator<EmitEvents, SocketData> {
+  public get volatile() {
     return this.sockets.volatile;
   }
 
   /**
    * Sets a modifier for a subsequent event emission that the event data will only be broadcast to the current node.
    *
-   * @return self
-   * @public
+   * @example
+   * // the “foo” event will be broadcast to all connected clients on this node
+   * io.local.emit("foo", "bar");
+   *
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public get local(): BroadcastOperator<EmitEvents, SocketData> {
+  public get local() {
     return this.sockets.local;
   }
 
   /**
-   * Adds a timeout in milliseconds for the next operation
-   *
-   * <pre><code>
+   * Adds a timeout in milliseconds for the next operation.
    *
+   * @example
    * io.timeout(1000).emit("some-event", (err, responses) => {
-   *   // ...
+   *   if (err) {
+   *     // some clients did not acknowledge the event in the given delay
+   *   } else {
+   *     console.log(responses); // one response per client
+   *   }
    * });
    *
-   * </pre></code>
-   *
    * @param timeout
    */
   public timeout(timeout: number) {
@@ -805,41 +1008,85 @@ export class Server<
   }
 
   /**
-   * Returns the matching socket instances
+   * Returns the matching socket instances.
    *
-   * @public
+   * Note: this method also works within a cluster of multiple Socket.IO servers, with a compatible {@link Adapter}.
+   *
+   * @example
+   * // return all Socket instances
+   * const sockets = await io.fetchSockets();
+   *
+   * // return all Socket instances in the "room1" room
+   * const sockets = await io.in("room1").fetchSockets();
+   *
+   * for (const socket of sockets) {
+   *   console.log(socket.id);
+   *   console.log(socket.handshake);
+   *   console.log(socket.rooms);
+   *   console.log(socket.data);
+   *
+   *   socket.emit("hello");
+   *   socket.join("room1");
+   *   socket.leave("room2");
+   *   socket.disconnect();
+   * }
    */
   public fetchSockets(): Promise<RemoteSocket<EmitEvents, SocketData>[]> {
     return this.sockets.fetchSockets();
   }
 
   /**
-   * Makes the matching socket instances join the specified rooms
+   * Makes the matching socket instances join the specified rooms.
    *
-   * @param room
-   * @public
+   * Note: this method also works within a cluster of multiple Socket.IO servers, with a compatible {@link Adapter}.
+   *
+   * @example
+   *
+   * // make all socket instances join the "room1" room
+   * io.socketsJoin("room1");
+   *
+   * // make all socket instances in the "room1" room join the "room2" and "room3" rooms
+   * io.in("room1").socketsJoin(["room2", "room3"]);
+   *
+   * @param room - a room, or an array of rooms
    */
-  public socketsJoin(room: Room | Room[]): void {
+  public socketsJoin(room: Room | Room[]) {
     return this.sockets.socketsJoin(room);
   }
 
   /**
-   * Makes the matching socket instances leave the specified rooms
+   * Makes the matching socket instances leave the specified rooms.
    *
-   * @param room
-   * @public
+   * Note: this method also works within a cluster of multiple Socket.IO servers, with a compatible {@link Adapter}.
+   *
+   * @example
+   * // make all socket instances leave the "room1" room
+   * io.socketsLeave("room1");
+   *
+   * // make all socket instances in the "room1" room leave the "room2" and "room3" rooms
+   * io.in("room1").socketsLeave(["room2", "room3"]);
+   *
+   * @param room - a room, or an array of rooms
    */
-  public socketsLeave(room: Room | Room[]): void {
+  public socketsLeave(room: Room | Room[]) {
     return this.sockets.socketsLeave(room);
   }
 
   /**
-   * Makes the matching socket instances disconnect
+   * Makes the matching socket instances disconnect.
+   *
+   * Note: this method also works within a cluster of multiple Socket.IO servers, with a compatible {@link Adapter}.
+   *
+   * @example
+   * // make all socket instances disconnect (the connections might be kept alive for other namespaces)
+   * io.disconnectSockets();
+   *
+   * // make all socket instances in the "room1" room disconnect and close the underlying connections
+   * io.in("room1").disconnectSockets(true);
    *
    * @param close - whether to close the underlying connection
-   * @public
    */
-  public disconnectSockets(close: boolean = false): void {
+  public disconnectSockets(close: boolean = false) {
     return this.sockets.disconnectSockets(close);
   }
 }
@@ -865,5 +1112,12 @@ module.exports.Server = Server;
 module.exports.Namespace = Namespace;
 module.exports.Socket = Socket;
 
-export { Socket, ServerOptions, Namespace, BroadcastOperator, RemoteSocket };
+export {
+  Socket,
+  DisconnectReason,
+  ServerOptions,
+  Namespace,
+  BroadcastOperator,
+  RemoteSocket,
+};
 export { Event } from "./socket";

lib/namespace.ts

@@ -6,11 +6,16 @@ import {
   EventsMap,
   StrictEventEmitter,
   DefaultEventsMap,
+  DecorateAcknowledgementsWithTimeoutAndMultipleResponses,
+  AllButLast,
+  Last,
+  FirstArg,
+  SecondArg,
 } from "./typed-events";
 import type { Client } from "./client";
 import debugModule from "debug";
 import type { Adapter, Room, SocketId } from "socket.io-adapter";
-import { BroadcastOperator, RemoteSocket } from "./broadcast-operator";
+import { BroadcastOperator } from "./broadcast-operator";
 
 const debug = debugModule("socket.io:namespace");
 
@@ -33,9 +38,9 @@ export interface NamespaceReservedEventsMap<
 }
 
 export interface ServerReservedEventsMap<
-  ListenEvents,
-  EmitEvents,
-  ServerSideEvents,
+  ListenEvents extends EventsMap,
+  EmitEvents extends EventsMap,
+  ServerSideEvents extends EventsMap,
   SocketData
 > extends NamespaceReservedEventsMap<
     ListenEvents,
@@ -52,6 +57,59 @@ export const RESERVED_EVENTS: ReadonlySet<string | Symbol> = new Set<
   keyof ServerReservedEventsMap<never, never, never, never>
 >(<const>["connect", "connection", "new_namespace"]);
 
+/**
+ * A Namespace is a communication channel that allows you to split the logic of your application over a single shared
+ * connection.
+ *
+ * Each namespace has its own:
+ *
+ * - event handlers
+ *
+ * ```
+ * io.of("/orders").on("connection", (socket) => {
+ *   socket.on("order:list", () => {});
+ *   socket.on("order:create", () => {});
+ * });
+ *
+ * io.of("/users").on("connection", (socket) => {
+ *   socket.on("user:list", () => {});
+ * });
+ * ```
+ *
+ * - rooms
+ *
+ * ```
+ * const orderNamespace = io.of("/orders");
+ *
+ * orderNamespace.on("connection", (socket) => {
+ *   socket.join("room1");
+ *   orderNamespace.to("room1").emit("hello");
+ * });
+ *
+ * const userNamespace = io.of("/users");
+ *
+ * userNamespace.on("connection", (socket) => {
+ *   socket.join("room1"); // distinct from the room in the "orders" namespace
+ *   userNamespace.to("room1").emit("holà");
+ * });
+ * ```
+ *
+ * - middlewares
+ *
+ * ```
+ * const orderNamespace = io.of("/orders");
+ *
+ * orderNamespace.use((socket, next) => {
+ *   // ensure the socket has access to the "orders" namespace
+ * });
+ *
+ * const userNamespace = io.of("/users");
+ *
+ * userNamespace.use((socket, next) => {
+ *   // ensure the socket has access to the "users" namespace
+ * });
+ * ```
+ */
 export class Namespace<
   ListenEvents extends EventsMap = DefaultEventsMap,
   EmitEvents extends EventsMap = ListenEvents,
@@ -123,10 +181,17 @@ export class Namespace<
   }
 
   /**
-   * Sets up namespace middleware.
+   * Registers a middleware, which is a function that gets executed for every incoming {@link Socket}.
    *
-   * @return self
-   * @public
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * myNamespace.use((socket, next) => {
+   *   // ...
+   *   next();
+   * });
+   *
+   * @param fn - the middleware function
    */
   public use(
     fn: (
@@ -171,36 +236,63 @@ export class Namespace<
   /**
    * Targets a room when emitting.
    *
-   * @param room
-   * @return self
-   * @public
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * // the “foo” event will be broadcast to all connected clients in the “room-101” room
+   * myNamespace.to("room-101").emit("foo", "bar");
+   *
+   * // with an array of rooms (a client will be notified at most once)
+   * myNamespace.to(["room-101", "room-102"]).emit("foo", "bar");
+   *
+   * // with multiple chained calls
+   * myNamespace.to("room-101").to("room-102").emit("foo", "bar");
+   *
+   * @param room - a room, or an array of rooms
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public to(room: Room | Room[]): BroadcastOperator<EmitEvents, SocketData> {
-    return new BroadcastOperator(this.adapter).to(room);
+  public to(room: Room | Room[]) {
+    return new BroadcastOperator<EmitEvents, SocketData>(this.adapter).to(room);
   }
 
   /**
-   * Targets a room when emitting.
+   * Targets a room when emitting. Similar to `to()`, but might feel clearer in some cases:
    *
-   * @param room
-   * @return self
-   * @public
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * // disconnect all clients in the "room-101" room
+   * myNamespace.in("room-101").disconnectSockets();
+   *
+   * @param room - a room, or an array of rooms
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public in(room: Room | Room[]): BroadcastOperator<EmitEvents, SocketData> {
-    return new BroadcastOperator(this.adapter).in(room);
+  public in(room: Room | Room[]) {
+    return new BroadcastOperator<EmitEvents, SocketData>(this.adapter).in(room);
   }
 
   /**
    * Excludes a room when emitting.
    *
-   * @param room
-   * @return self
-   * @public
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * // the "foo" event will be broadcast to all connected clients, except the ones that are in the "room-101" room
+   * myNamespace.except("room-101").emit("foo", "bar");
+   *
+   * // with an array of rooms
+   * myNamespace.except(["room-101", "room-102"]).emit("foo", "bar");
+   *
+   * // with multiple chained calls
+   * myNamespace.except("room-101").except("room-102").emit("foo", "bar");
+   *
+   * @param room - a room, or an array of rooms
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public except(
-    room: Room | Room[]
-  ): BroadcastOperator<EmitEvents, SocketData> {
-    return new BroadcastOperator(this.adapter).except(room);
+  public except(room: Room | Room[]) {
+    return new BroadcastOperator<EmitEvents, SocketData>(this.adapter).except(
+      room
+    );
   }
 
   /**
@@ -209,46 +301,96 @@ export class Namespace<
    * @return {Socket}
    * @private
    */
-  _add(
+  async _add(
     client: Client<ListenEvents, EmitEvents, ServerSideEvents>,
-    query,
-    fn?: () => void
-  ): Socket<ListenEvents, EmitEvents, ServerSideEvents, SocketData> {
+    auth: Record<string, unknown>,
+    fn: (
+      socket: Socket<ListenEvents, EmitEvents, ServerSideEvents, SocketData>
+    ) => void
+  ) {
     debug("adding socket to nsp %s", this.name);
-    const socket = new Socket(this, client, query);
+    const socket = await this._createSocket(client, auth);
+
+    if (
+      // @ts-ignore
+      this.server.opts.connectionStateRecovery?.skipMiddlewares &&
+      socket.recovered &&
+      client.conn.readyState === "open"
+    ) {
+      return this._doConnect(socket, fn);
+    }
+
     this.run(socket, (err) => {
       process.nextTick(() => {
-        if ("open" == client.conn.readyState) {
-          if (err) {
-            if (client.conn.protocol === 3) {
-              return socket._error(err.data || err.message);
-            } else {
-              return socket._error({
-                message: err.message,
-                data: err.data,
-              });
-            }
-          }
-
-          // track socket
-          this.sockets.set(socket.id, socket);
-
-          // it's paramount that the internal `onconnect` logic
-          // fires before user-set events to prevent state order
-          // violations (such as a disconnection before the connection
-          // logic is complete)
-          socket._onconnect();
-          if (fn) fn();
-
-          // fire user-set events
-          this.emitReserved("connect", socket);
-          this.emitReserved("connection", socket);
-        } else {
+        if ("open" !== client.conn.readyState) {
           debug("next called after client was closed - ignoring socket");
+          socket._cleanup();
+          return;
         }
+
+        if (err) {
+          debug("middleware error, sending CONNECT_ERROR packet to the client");
+          socket._cleanup();
+          if (client.conn.protocol === 3) {
+            return socket._error(err.data || err.message);
+          } else {
+            return socket._error({
+              message: err.message,
+              data: err.data,
+            });
+          }
+        }
+
+        this._doConnect(socket, fn);
       });
     });
-    return socket;
+  }
+
+  private async _createSocket(
+    client: Client<ListenEvents, EmitEvents, ServerSideEvents>,
+    auth: Record<string, unknown>
+  ) {
+    const sessionId = auth.pid;
+    const offset = auth.offset;
+    if (
+      // @ts-ignore
+      this.server.opts.connectionStateRecovery &&
+      typeof sessionId === "string" &&
+      typeof offset === "string"
+    ) {
+      let session;
+      try {
+        session = await this.adapter.restoreSession(sessionId, offset);
+      } catch (e) {
+        debug("error while restoring session: %s", e);
+      }
+      if (session) {
+        debug("connection state recovered for sid %s", session.sid);
+        return new Socket(this, client, auth, session);
+      }
+    }
+    return new Socket(this, client, auth);
+  }
+
+  private _doConnect(
+    socket: Socket<ListenEvents, EmitEvents, ServerSideEvents, SocketData>,
+    fn: (
+      socket: Socket<ListenEvents, EmitEvents, ServerSideEvents, SocketData>
+    ) => void
+  ) {
+    // track socket
+    this.sockets.set(socket.id, socket);
+
+    // it's paramount that the internal `onconnect` logic
+    // fires before user-set events to prevent state order
+    // violations (such as a disconnection before the connection
+    // logic is complete)
+    socket._onconnect();
+    if (fn) fn(socket);
+
+    // fire user-set events
+    this.emitReserved("connect", socket);
+    this.emitReserved("connection", socket);
   }
 
   /**
@@ -267,10 +409,26 @@ export class Namespace<
   }
 
   /**
-   * Emits to all clients.
+   * Emits to all connected clients.
+   *
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * myNamespace.emit("hello", "world");
+   *
+   * // all serializable datastructures are supported (no need to call JSON.stringify)
+   * myNamespace.emit("hello", 1, "2", { 3: ["4"], 5: Uint8Array.from([6]) });
+   *
+   * // with an acknowledgement from the clients
+   * myNamespace.timeout(1000).emit("some-event", (err, responses) => {
+   *   if (err) {
+   *     // some clients did not acknowledge the event in the given delay
+   *   } else {
+   *     console.log(responses); // one response per client
+   *   }
+   * });
    *
    * @return Always true
-   * @public
    */
   public emit<Ev extends EventNames<EmitEvents>>(
     ev: Ev,
@@ -282,11 +440,46 @@ export class Namespace<
     );
   }
 
+  /**
+   * Emits an event and waits for an acknowledgement from all clients.
+   *
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * try {
+   *   const responses = await myNamespace.timeout(1000).emitWithAck("some-event");
+   *   console.log(responses); // one response per client
+   * } catch (e) {
+   *   // some clients did not acknowledge the event in the given delay
+   * }
+   *
+   * @return a Promise that will be fulfilled when all clients have acknowledged the event
+   */
+  public emitWithAck<Ev extends EventNames<EmitEvents>>(
+    ev: Ev,
+    ...args: AllButLast<EventParams<EmitEvents, Ev>>
+  ): Promise<SecondArg<Last<EventParams<EmitEvents, Ev>>>> {
+    return new BroadcastOperator<EmitEvents, SocketData>(
+      this.adapter
+    ).emitWithAck(ev, ...args);
+  }
+
   /**
    * Sends a `message` event to all clients.
    *
+   * This method mimics the WebSocket.send() method.
+   *
+   * @see https://developer.mozilla.org/en-US/docs/Web/API/WebSocket/send
+   *
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * myNamespace.send("hello");
+   *
+   * // this is equivalent to
+   * myNamespace.emit("message", "hello");
+   *
    * @return self
-   * @public
    */
   public send(...args: EventParams<EmitEvents, "message">): this {
     this.emit("message", ...args);
@@ -294,10 +487,9 @@ export class Namespace<
   }
 
   /**
-   * Sends a `message` event to all clients.
+   * Sends a `message` event to all clients. Sends a `message` event. Alias of {@link send}.
    *
    * @return self
-   * @public
    */
   public write(...args: EventParams<EmitEvents, "message">): this {
     this.emit("message", ...args);
@@ -305,24 +497,86 @@ export class Namespace<
   }
 
   /**
-   * Emit a packet to other Socket.IO servers
+   * Sends a message to the other Socket.IO servers of the cluster.
+   *
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * myNamespace.serverSideEmit("hello", "world");
+   *
+   * myNamespace.on("hello", (arg1) => {
+   *   console.log(arg1); // prints "world"
+   * });
+   *
+   * // acknowledgements (without binary content) are supported too:
+   * myNamespace.serverSideEmit("ping", (err, responses) => {
+   *  if (err) {
+   *     // some servers did not acknowledge the event in the given delay
+   *   } else {
+   *     console.log(responses); // one response per server (except the current one)
+   *   }
+   * });
+   *
+   * myNamespace.on("ping", (cb) => {
+   *   cb("pong");
+   * });
    *
    * @param ev - the event name
    * @param args - an array of arguments, which may include an acknowledgement callback at the end
-   * @public
    */
   public serverSideEmit<Ev extends EventNames<ServerSideEvents>>(
     ev: Ev,
-    ...args: EventParams<ServerSideEvents, Ev>
+    ...args: EventParams<
+      DecorateAcknowledgementsWithTimeoutAndMultipleResponses<ServerSideEvents>,
+      Ev
+    >
   ): boolean {
     if (RESERVED_EVENTS.has(ev)) {
-      throw new Error(`"${ev}" is a reserved event name`);
+      throw new Error(`"${String(ev)}" is a reserved event name`);
     }
     args.unshift(ev);
     this.adapter.serverSideEmit(args);
     return true;
   }
 
+  /**
+   * Sends a message and expect an acknowledgement from the other Socket.IO servers of the cluster.
+   *
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * try {
+   *   const responses = await myNamespace.serverSideEmitWithAck("ping");
+   *   console.log(responses); // one response per server (except the current one)
+   * } catch (e) {
+   *   // some servers did not acknowledge the event in the given delay
+   * }
+   *
+   * @param ev - the event name
+   * @param args - an array of arguments
+   *
+   * @return a Promise that will be fulfilled when all servers have acknowledged the event
+   */
+  public serverSideEmitWithAck<Ev extends EventNames<ServerSideEvents>>(
+    ev: Ev,
+    ...args: AllButLast<EventParams<ServerSideEvents, Ev>>
+  ): Promise<FirstArg<Last<EventParams<ServerSideEvents, Ev>>>[]> {
+    return new Promise((resolve, reject) => {
+      args.push((err, responses) => {
+        if (err) {
+          err.responses = responses;
+          return reject(err);
+        } else {
+          return resolve(responses);
+        }
+      });
+      this.serverSideEmit(
+        ev,
+        ...(args as any[] as EventParams<ServerSideEvents, Ev>)
+      );
+    });
+  }
+
   /**
    * Called when a packet is received from another Socket.IO server
    *
@@ -337,24 +591,30 @@ export class Namespace<
   /**
    * Gets a list of clients.
    *
-   * @return self
-   * @public
+   * @deprecated this method will be removed in the next major release, please use {@link Namespace#serverSideEmit} or
+   * {@link Namespace#fetchSockets} instead.
    */
   public allSockets(): Promise<Set<SocketId>> {
-    return new BroadcastOperator(this.adapter).allSockets();
+    return new BroadcastOperator<EmitEvents, SocketData>(
+      this.adapter
+    ).allSockets();
   }
 
   /**
    * Sets the compress flag.
    *
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * myNamespace.compress(false).emit("hello");
+   *
    * @param compress - if `true`, compresses the sending data
    * @return self
-   * @public
    */
-  public compress(
-    compress: boolean
-  ): BroadcastOperator<EmitEvents, SocketData> {
-    return new BroadcastOperator(this.adapter).compress(compress);
+  public compress(compress: boolean) {
+    return new BroadcastOperator<EmitEvents, SocketData>(this.adapter).compress(
+      compress
+    );
   }
 
   /**
@@ -362,76 +622,149 @@ export class Namespace<
    * receive messages (because of network slowness or other issues, or because they’re connected through long polling
    * and is in the middle of a request-response cycle).
    *
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * myNamespace.volatile.emit("hello"); // the clients may or may not receive it
+   *
    * @return self
-   * @public
    */
-  public get volatile(): BroadcastOperator<EmitEvents, SocketData> {
-    return new BroadcastOperator(this.adapter).volatile;
+  public get volatile() {
+    return new BroadcastOperator<EmitEvents, SocketData>(this.adapter).volatile;
   }
 
   /**
    * Sets a modifier for a subsequent event emission that the event data will only be broadcast to the current node.
    *
-   * @return self
-   * @public
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * // the “foo” event will be broadcast to all connected clients on this node
+   * myNamespace.local.emit("foo", "bar");
+   *
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public get local(): BroadcastOperator<EmitEvents, SocketData> {
-    return new BroadcastOperator(this.adapter).local;
+  public get local() {
+    return new BroadcastOperator<EmitEvents, SocketData>(this.adapter).local;
   }
 
   /**
-   * Adds a timeout in milliseconds for the next operation
+   * Adds a timeout in milliseconds for the next operation.
    *
-   * <pre><code>
+   * @example
+   * const myNamespace = io.of("/my-namespace");
    *
-   * io.timeout(1000).emit("some-event", (err, responses) => {
-   *   // ...
+   * myNamespace.timeout(1000).emit("some-event", (err, responses) => {
+   *   if (err) {
+   *     // some clients did not acknowledge the event in the given delay
+   *   } else {
+   *     console.log(responses); // one response per client
+   *   }
    * });
    *
-   * </pre></code>
-   *
    * @param timeout
    */
   public timeout(timeout: number) {
-    return new BroadcastOperator(this.adapter).timeout(timeout);
+    return new BroadcastOperator<EmitEvents, SocketData>(this.adapter).timeout(
+      timeout
+    );
   }
 
   /**
-   * Returns the matching socket instances
+   * Returns the matching socket instances.
    *
-   * @public
-   */
-  public fetchSockets(): Promise<RemoteSocket<EmitEvents, SocketData>[]> {
-    return new BroadcastOperator(this.adapter).fetchSockets();
-  }
-
-  /**
-   * Makes the matching socket instances join the specified rooms
+   * Note: this method also works within a cluster of multiple Socket.IO servers, with a compatible {@link Adapter}.
    *
-   * @param room
-   * @public
-   */
-  public socketsJoin(room: Room | Room[]): void {
-    return new BroadcastOperator(this.adapter).socketsJoin(room);
-  }
-
-  /**
-   * Makes the matching socket instances leave the specified rooms
+   * @example
+   * const myNamespace = io.of("/my-namespace");
    *
-   * @param room
-   * @public
+   * // return all Socket instances
+   * const sockets = await myNamespace.fetchSockets();
+   *
+   * // return all Socket instances in the "room1" room
+   * const sockets = await myNamespace.in("room1").fetchSockets();
+   *
+   * for (const socket of sockets) {
+   *   console.log(socket.id);
+   *   console.log(socket.handshake);
+   *   console.log(socket.rooms);
+   *   console.log(socket.data);
+   *
+   *   socket.emit("hello");
+   *   socket.join("room1");
+   *   socket.leave("room2");
+   *   socket.disconnect();
+   * }
    */
-  public socketsLeave(room: Room | Room[]): void {
-    return new BroadcastOperator(this.adapter).socketsLeave(room);
+  public fetchSockets() {
+    return new BroadcastOperator<EmitEvents, SocketData>(
+      this.adapter
+    ).fetchSockets();
   }
 
   /**
-   * Makes the matching socket instances disconnect
+   * Makes the matching socket instances join the specified rooms.
+   *
+   * Note: this method also works within a cluster of multiple Socket.IO servers, with a compatible {@link Adapter}.
+   *
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * // make all socket instances join the "room1" room
+   * myNamespace.socketsJoin("room1");
+   *
+   * // make all socket instances in the "room1" room join the "room2" and "room3" rooms
+   * myNamespace.in("room1").socketsJoin(["room2", "room3"]);
+   *
+   * @param room - a room, or an array of rooms
+   */
+  public socketsJoin(room: Room | Room[]) {
+    return new BroadcastOperator<EmitEvents, SocketData>(
+      this.adapter
+    ).socketsJoin(room);
+  }
+
+  /**
+   * Makes the matching socket instances leave the specified rooms.
+   *
+   * Note: this method also works within a cluster of multiple Socket.IO servers, with a compatible {@link Adapter}.
+   *
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * // make all socket instances leave the "room1" room
+   * myNamespace.socketsLeave("room1");
+   *
+   * // make all socket instances in the "room1" room leave the "room2" and "room3" rooms
+   * myNamespace.in("room1").socketsLeave(["room2", "room3"]);
+   *
+   * @param room - a room, or an array of rooms
+   */
+  public socketsLeave(room: Room | Room[]) {
+    return new BroadcastOperator<EmitEvents, SocketData>(
+      this.adapter
+    ).socketsLeave(room);
+  }
+
+  /**
+   * Makes the matching socket instances disconnect.
+   *
+   * Note: this method also works within a cluster of multiple Socket.IO servers, with a compatible {@link Adapter}.
+   *
+   * @example
+   * const myNamespace = io.of("/my-namespace");
+   *
+   * // make all socket instances disconnect (the connections might be kept alive for other namespaces)
+   * myNamespace.disconnectSockets();
+   *
+   * // make all socket instances in the "room1" room disconnect and close the underlying connections
+   * myNamespace.in("room1").disconnectSockets(true);
    *
    * @param close - whether to close the underlying connection
-   * @public
    */
-  public disconnectSockets(close: boolean = false): void {
-    return new BroadcastOperator(this.adapter).disconnectSockets(close);
+  public disconnectSockets(close: boolean = false) {
+    return new BroadcastOperator<EmitEvents, SocketData>(
+      this.adapter
+    ).disconnectSockets(close);
   }
 }

lib/parent-namespace.ts

@@ -7,7 +7,25 @@ import type {
   DefaultEventsMap,
 } from "./typed-events";
 import type { BroadcastOptions } from "socket.io-adapter";
+import debugModule from "debug";
 
+const debug = debugModule("socket.io:parent-namespace");
+
+/**
+ * A parent namespace is a special {@link Namespace} that holds a list of child namespaces which were created either
+ * with a regular expression or with a function.
+ *
+ * @example
+ * const parentNamespace = io.of(/\/dynamic-\d+/);
+ *
+ * parentNamespace.on("connection", (socket) => {
+ *   const childNamespace = socket.nsp;
+ * }
+ *
+ * // will reach all the clients that are in one of the child namespaces, like "/dynamic-101"
+ * parentNamespace.emit("hello", "world");
+ *
+ */
 export class ParentNamespace<
   ListenEvents extends EventsMap = DefaultEventsMap,
   EmitEvents extends EventsMap = ListenEvents,
@@ -52,6 +70,7 @@ export class ParentNamespace<
   createChild(
     name: string
   ): Namespace<ListenEvents, EmitEvents, ServerSideEvents, SocketData> {
+    debug("creating child namespace %s", name);
     const namespace = new Namespace(this.server, name);
     namespace._fns = this._fns.slice(0);
     this.listeners("connect").forEach((listener) =>
@@ -61,7 +80,26 @@ export class ParentNamespace<
       namespace.on("connection", listener)
     );
     this.children.add(namespace);
+
+    if (this.server._opts.cleanupEmptyChildNamespaces) {
+      const remove = namespace._remove;
+
+      namespace._remove = (socket) => {
+        remove.call(namespace, socket);
+        if (namespace.sockets.size === 0) {
+          debug("closing child namespace %s", name);
+          namespace.adapter.close();
+          this.server._nsps.delete(namespace.name);
+          this.children.delete(namespace);
+        }
+      };
+    }
+
     this.server._nsps.set(name, namespace);
+
+    // @ts-ignore
+    this.server.sockets.emitReserved("new_namespace", namespace);
+
     return namespace;
   }
 

lib/socket.ts

@@ -2,19 +2,26 @@ import { Packet, PacketType } from "socket.io-parser";
 import debugModule from "debug";
 import type { Server } from "./index";
 import {
-  EventParams,
-  EventNames,
-  EventsMap,
-  StrictEventEmitter,
+  AllButLast,
+  DecorateAcknowledgements,
+  DecorateAcknowledgementsWithMultipleResponses,
   DefaultEventsMap,
+  EventNames,
+  EventParams,
+  EventsMap,
+  FirstArg,
+  Last,
+  StrictEventEmitter,
 } from "./typed-events";
 import type { Client } from "./client";
 import type { Namespace, NamespaceReservedEventsMap } from "./namespace";
-import type { IncomingMessage, IncomingHttpHeaders } from "http";
+import type { IncomingHttpHeaders, IncomingMessage } from "http";
 import type {
   Adapter,
   BroadcastFlags,
+  PrivateSessionId,
   Room,
+  Session,
   SocketId,
 } from "socket.io-adapter";
 import base64id from "base64id";
@@ -25,9 +32,32 @@ const debug = debugModule("socket.io:socket");
 
 type ClientReservedEvents = "connect_error";
 
+// TODO for next major release: cleanup disconnect reasons
+export type DisconnectReason =
+  // Engine.IO close reasons
+  | "transport error"
+  | "transport close"
+  | "forced close"
+  | "ping timeout"
+  | "parse error"
+  // Socket.IO disconnect reasons
+  | "server shutting down"
+  | "forced server close"
+  | "client namespace disconnect"
+  | "server namespace disconnect";
+
+const RECOVERABLE_DISCONNECT_REASONS: ReadonlySet<DisconnectReason> = new Set([
+  "transport error",
+  "transport close",
+  "forced close",
+  "ping timeout",
+  "server shutting down",
+  "forced server close",
+]);
+
 export interface SocketReservedEventsMap {
-  disconnect: (reason: string) => void;
-  disconnecting: (reason: string) => void;
+  disconnect: (reason: DisconnectReason, description?: any) => void;
+  disconnecting: (reason: DisconnectReason, description?: any) => void;
   error: (err: Error) => void;
 }
 
@@ -112,6 +142,39 @@ export interface Handshake {
  */
 export type Event = [string, ...any[]];
 
+function noop() {}
+
+/**
+ * This is the main object for interacting with a client.
+ *
+ * A Socket belongs to a given {@link Namespace} and uses an underlying {@link Client} to communicate.
+ *
+ * Within each {@link Namespace}, you can also define arbitrary channels (called "rooms") that the {@link Socket} can
+ * join and leave. That provides a convenient way to broadcast to a group of socket instances.
+ *
+ * @example
+ * io.on("connection", (socket) => {
+ *   console.log(`socket ${socket.id} connected`);
+ *
+ *   // send an event to the client
+ *   socket.emit("foo", "bar");
+ *
+ *   socket.on("foobar", () => {
+ *     // an event was received from the client
+ *   });
+ *
+ *   // join the room named "room1"
+ *   socket.join("room1");
+ *
+ *   // broadcast to everyone in the room named "room1"
+ *   io.to("room1").emit("hello");
+ *
+ *   // upon disconnection
+ *   socket.on("disconnect", (reason) => {
+ *     console.log(`socket ${socket.id} disconnected due to ${reason}`);
+ *   });
+ * });
+ */
 export class Socket<
   ListenEvents extends EventsMap = DefaultEventsMap,
   EmitEvents extends EventsMap = ListenEvents,
@@ -122,15 +185,47 @@ export class Socket<
   EmitEvents,
   SocketReservedEventsMap
 > {
+  /**
+   * An unique identifier for the session.
+   */
   public readonly id: SocketId;
+  /**
+   * Whether the connection state was recovered after a temporary disconnection. In that case, any missed packets will
+   * be transmitted to the client, the data attribute and the rooms will be restored.
+   */
+  public readonly recovered: boolean = false;
+  /**
+   * The handshake details.
+   */
   public readonly handshake: Handshake;
   /**
-   * Additional information that can be attached to the Socket instance and which will be used in the fetchSockets method
+   * Additional information that can be attached to the Socket instance and which will be used in the
+   * {@link Server.fetchSockets()} method.
    */
   public data: Partial<SocketData> = {};
-
+  /**
+   * Whether the socket is currently connected or not.
+   *
+   * @example
+   * io.use((socket, next) => {
+   *   console.log(socket.connected); // false
+   *   next();
+   * });
+   *
+   * io.on("connection", (socket) => {
+   *   console.log(socket.connected); // true
+   * });
+   */
   public connected: boolean = false;
 
+  /**
+   * The session ID, which must not be shared (unlike {@link id}).
+   *
+   * @private
+   */
+  private readonly pid: PrivateSessionId;
+
+  // TODO: remove this unused reference
   private readonly server: Server<
     ListenEvents,
     EmitEvents,
@@ -155,16 +250,34 @@ export class Socket<
   constructor(
     readonly nsp: Namespace<ListenEvents, EmitEvents, ServerSideEvents>,
     readonly client: Client<ListenEvents, EmitEvents, ServerSideEvents>,
-    auth: object
+    auth: Record<string, unknown>,
+    previousSession?: Session
   ) {
     super();
     this.server = nsp.server;
     this.adapter = this.nsp.adapter;
-    if (client.conn.protocol === 3) {
-      // @ts-ignore
-      this.id = nsp.name !== "/" ? nsp.name + "#" + client.id : client.id;
+    if (previousSession) {
+      this.id = previousSession.sid;
+      this.pid = previousSession.pid;
+      previousSession.rooms.forEach((room) => this.join(room));
+      this.data = previousSession.data as Partial<SocketData>;
+      previousSession.missedPackets.forEach((packet) => {
+        this.packet({
+          type: PacketType.EVENT,
+          data: packet,
+        });
+      });
+      this.recovered = true;
     } else {
-      this.id = base64id.generateId(); // don't reuse the Engine.IO id because it's sensitive information
+      if (client.conn.protocol === 3) {
+        // @ts-ignore
+        this.id = nsp.name !== "/" ? nsp.name + "#" + client.id : client.id;
+      } else {
+        this.id = base64id.generateId(); // don't reuse the Engine.IO id because it's sensitive information
+      }
+      if (this.server._opts.connectionStateRecovery) {
+        this.pid = base64id.generateId();
+      }
     }
     this.handshake = this.buildHandshake(auth);
   }
@@ -193,15 +306,27 @@ export class Socket<
   /**
    * Emits to this client.
    *
+   * @example
+   * io.on("connection", (socket) => {
+   *   socket.emit("hello", "world");
+   *
+   *   // all serializable datastructures are supported (no need to call JSON.stringify)
+   *   socket.emit("hello", 1, "2", { 3: ["4"], 5: Buffer.from([6]) });
+   *
+   *   // with an acknowledgement from the client
+   *   socket.emit("hello", "world", (val) => {
+   *     // ...
+   *   });
+   * });
+   *
    * @return Always returns `true`.
-   * @public
    */
   public emit<Ev extends EventNames<EmitEvents>>(
     ev: Ev,
     ...args: EventParams<EmitEvents, Ev>
   ): boolean {
     if (RESERVED_EVENTS.has(ev)) {
-      throw new Error(`"${ev}" is a reserved event name`);
+      throw new Error(`"${String(ev)}" is a reserved event name`);
     }
     const data: any[] = [ev, ...args];
     const packet: any = {
@@ -221,12 +346,58 @@ export class Socket<
     const flags = Object.assign({}, this.flags);
     this.flags = {};
 
-    this.notifyOutgoingListeners(packet);
-    this.packet(packet, flags);
+    // @ts-ignore
+    if (this.nsp.server.opts.connectionStateRecovery) {
+      // this ensures the packet is stored and can be transmitted upon reconnection
+      this.adapter.broadcast(packet, {
+        rooms: new Set([this.id]),
+        except: new Set(),
+        flags,
+      });
+    } else {
+      this.notifyOutgoingListeners(packet);
+      this.packet(packet, flags);
+    }
 
     return true;
   }
 
+  /**
+   * Emits an event and waits for an acknowledgement
+   *
+   * @example
+   * io.on("connection", async (socket) => {
+   *   // without timeout
+   *   const response = await socket.emitWithAck("hello", "world");
+   *
+   *   // with a specific timeout
+   *   try {
+   *     const response = await socket.timeout(1000).emitWithAck("hello", "world");
+   *   } catch (err) {
+   *     // the client did not acknowledge the event in the given delay
+   *   }
+   * });
+   *
+   * @return a Promise that will be fulfilled when the client acknowledges the event
+   */
+  public emitWithAck<Ev extends EventNames<EmitEvents>>(
+    ev: Ev,
+    ...args: AllButLast<EventParams<EmitEvents, Ev>>
+  ): Promise<FirstArg<Last<EventParams<EmitEvents, Ev>>>> {
+    // the timeout flag is optional
+    const withErr = this.flags.timeout !== undefined;
+    return new Promise((resolve, reject) => {
+      args.push((arg1, arg2) => {
+        if (withErr) {
+          return arg1 ? reject(arg1) : resolve(arg2);
+        } else {
+          return resolve(arg1);
+        }
+      });
+      this.emit(ev, ...(args as any[] as EventParams<EmitEvents, Ev>));
+    });
+  }
+
   /**
    * @private
    */
@@ -252,43 +423,83 @@ export class Socket<
   /**
    * Targets a room when broadcasting.
    *
-   * @param room
-   * @return self
-   * @public
+   * @example
+   * io.on("connection", (socket) => {
+   *   // the “foo” event will be broadcast to all connected clients in the “room-101” room, except this socket
+   *   socket.to("room-101").emit("foo", "bar");
+   *
+   *   // the code above is equivalent to:
+   *   io.to("room-101").except(socket.id).emit("foo", "bar");
+   *
+   *   // with an array of rooms (a client will be notified at most once)
+   *   socket.to(["room-101", "room-102"]).emit("foo", "bar");
+   *
+   *   // with multiple chained calls
+   *   socket.to("room-101").to("room-102").emit("foo", "bar");
+   * });
+   *
+   * @param room - a room, or an array of rooms
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public to(room: Room | Room[]): BroadcastOperator<EmitEvents, SocketData> {
+  public to(room: Room | Room[]) {
     return this.newBroadcastOperator().to(room);
   }
 
   /**
-   * Targets a room when broadcasting.
+   * Targets a room when broadcasting. Similar to `to()`, but might feel clearer in some cases:
    *
-   * @param room
-   * @return self
-   * @public
+   * @example
+   * io.on("connection", (socket) => {
+   *   // disconnect all clients in the "room-101" room, except this socket
+   *   socket.in("room-101").disconnectSockets();
+   * });
+   *
+   * @param room - a room, or an array of rooms
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public in(room: Room | Room[]): BroadcastOperator<EmitEvents, SocketData> {
+  public in(room: Room | Room[]) {
     return this.newBroadcastOperator().in(room);
   }
 
   /**
    * Excludes a room when broadcasting.
    *
-   * @param room
-   * @return self
-   * @public
+   * @example
+   * io.on("connection", (socket) => {
+   *   // the "foo" event will be broadcast to all connected clients, except the ones that are in the "room-101" room
+   *   // and this socket
+   *   socket.except("room-101").emit("foo", "bar");
+   *
+   *   // with an array of rooms
+   *   socket.except(["room-101", "room-102"]).emit("foo", "bar");
+   *
+   *   // with multiple chained calls
+   *   socket.except("room-101").except("room-102").emit("foo", "bar");
+   * });
+   *
+   * @param room - a room, or an array of rooms
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public except(
-    room: Room | Room[]
-  ): BroadcastOperator<EmitEvents, SocketData> {
+  public except(room: Room | Room[]) {
     return this.newBroadcastOperator().except(room);
   }
 
   /**
    * Sends a `message` event.
    *
+   * This method mimics the WebSocket.send() method.
+   *
+   * @see https://developer.mozilla.org/en-US/docs/Web/API/WebSocket/send
+   *
+   * @example
+   * io.on("connection", (socket) => {
+   *   socket.send("hello");
+   *
+   *   // this is equivalent to
+   *   socket.emit("message", "hello");
+   * });
+   *
    * @return self
-   * @public
    */
   public send(...args: EventParams<EmitEvents, "message">): this {
     this.emit("message", ...args);
@@ -296,10 +507,9 @@ export class Socket<
   }
 
   /**
-   * Sends a `message` event.
+   * Sends a `message` event. Alias of {@link send}.
    *
    * @return self
-   * @public
    */
   public write(...args: EventParams<EmitEvents, "message">): this {
     this.emit("message", ...args);
@@ -325,9 +535,17 @@ export class Socket<
   /**
    * Joins a room.
    *
+   * @example
+   * io.on("connection", (socket) => {
+   *   // join a single room
+   *   socket.join("room1");
+   *
+   *   // join multiple rooms
+   *   socket.join(["room1", "room2"]);
+   * });
+   *
    * @param {String|Array} rooms - room or array of rooms
    * @return a Promise or nothing, depending on the adapter
-   * @public
    */
   public join(rooms: Room | Array<Room>): Promise<void> | void {
     debug("join room %s", rooms);
@@ -341,9 +559,17 @@ export class Socket<
   /**
    * Leaves a room.
    *
+   * @example
+   * io.on("connection", (socket) => {
+   *   // leave a single room
+   *   socket.leave("room1");
+   *
+   *   // leave multiple rooms
+   *   socket.leave("room1").leave("room2");
+   * });
+   *
    * @param {String} room
    * @return a Promise or nothing, depending on the adapter
-   * @public
    */
   public leave(room: string): Promise<void> | void {
     debug("leave room %s", room);
@@ -375,7 +601,10 @@ export class Socket<
     if (this.conn.protocol === 3) {
       this.packet({ type: PacketType.CONNECT });
     } else {
-      this.packet({ type: PacketType.CONNECT, data: { sid: this.id } });
+      this.packet({
+        type: PacketType.CONNECT,
+        data: { sid: this.id, pid: this.pid },
+      });
     }
   }
 
@@ -503,22 +732,47 @@ export class Socket<
    * Called upon closing. Called by `Client`.
    *
    * @param {String} reason
+   * @param description
    * @throw {Error} optional error object
    *
    * @private
    */
-  _onclose(reason: string): this | undefined {
+  _onclose(reason: DisconnectReason, description?: any): this | undefined {
     if (!this.connected) return this;
     debug("closing socket - reason %s", reason);
-    this.emitReserved("disconnecting", reason);
-    this.leaveAll();
+    this.emitReserved("disconnecting", reason, description);
+
+    if (
+      this.server._opts.connectionStateRecovery &&
+      RECOVERABLE_DISCONNECT_REASONS.has(reason)
+    ) {
+      debug("connection state recovery is enabled for sid %s", this.id);
+      this.adapter.persistSession({
+        sid: this.id,
+        pid: this.pid,
+        rooms: [...this.rooms],
+        data: this.data,
+      });
+    }
+
+    this._cleanup();
     this.nsp._remove(this);
     this.client._remove(this);
     this.connected = false;
-    this.emitReserved("disconnect", reason);
+    this.emitReserved("disconnect", reason, description);
     return;
   }
 
+  /**
+   * Makes the socket leave all the rooms it was part of and prevents it from joining any other room
+   *
+   * @private
+   */
+  _cleanup() {
+    this.leaveAll();
+    this.join = noop;
+  }
+
   /**
    * Produces an `error` packet.
    *
@@ -533,10 +787,17 @@ export class Socket<
   /**
    * Disconnects this client.
    *
-   * @param {Boolean} close - if `true`, closes the underlying connection
-   * @return {Socket} self
+   * @example
+   * io.on("connection", (socket) => {
+   *   // disconnect this socket (the connection might be kept alive for other namespaces)
+   *   socket.disconnect();
    *
-   * @public
+   *   // disconnect this socket and close the underlying connection
+   *   socket.disconnect(true);
+   * })
+   *
+   * @param {Boolean} close - if `true`, closes the underlying connection
+   * @return self
    */
   public disconnect(close = false): this {
     if (!this.connected) return this;
@@ -552,9 +813,13 @@ export class Socket<
   /**
    * Sets the compress flag.
    *
+   * @example
+   * io.on("connection", (socket) => {
+   *   socket.compress(false).emit("hello");
+   * });
+   *
    * @param {Boolean} compress - if `true`, compresses the sending data
    * @return {Socket} self
-   * @public
    */
   public compress(compress: boolean): this {
     this.flags.compress = compress;
@@ -566,8 +831,12 @@ export class Socket<
    * receive messages (because of network slowness or other issues, or because they’re connected through long polling
    * and is in the middle of a request-response cycle).
    *
+   * @example
+   * io.on("connection", (socket) => {
+   *   socket.volatile.emit("hello"); // the client may or may not receive it
+   * });
+   *
    * @return {Socket} self
-   * @public
    */
   public get volatile(): this {
     this.flags.volatile = true;
@@ -578,20 +847,30 @@ export class Socket<
    * Sets a modifier for a subsequent event emission that the event data will only be broadcast to every sockets but the
    * sender.
    *
-   * @return {Socket} self
-   * @public
+   * @example
+   * io.on("connection", (socket) => {
+   *   // the “foo” event will be broadcast to all connected clients, except this socket
+   *   socket.broadcast.emit("foo", "bar");
+   * });
+   *
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public get broadcast(): BroadcastOperator<EmitEvents, SocketData> {
+  public get broadcast() {
     return this.newBroadcastOperator();
   }
 
   /**
    * Sets a modifier for a subsequent event emission that the event data will only be broadcast to the current node.
    *
-   * @return {Socket} self
-   * @public
+   * @example
+   * io.on("connection", (socket) => {
+   *   // the “foo” event will be broadcast to all connected clients on this node, except this socket
+   *   socket.local.emit("foo", "bar");
+   * });
+   *
+   * @return a new {@link BroadcastOperator} instance for chaining
    */
-  public get local(): BroadcastOperator<EmitEvents, SocketData> {
+  public get local() {
     return this.newBroadcastOperator().local;
   }
 
@@ -599,18 +878,25 @@ export class Socket<
    * Sets a modifier for a subsequent event emission that the callback will be called with an error when the
    * given number of milliseconds have elapsed without an acknowledgement from the client:
    *
-   * ```
-   * socket.timeout(5000).emit("my-event", (err) => {
-   *   if (err) {
-   *     // the client did not acknowledge the event in the given delay
-   *   }
+   * @example
+   * io.on("connection", (socket) => {
+   *   socket.timeout(5000).emit("my-event", (err) => {
+   *     if (err) {
+   *       // the client did not acknowledge the event in the given delay
+   *     }
+   *   });
    * });
-   * ```
    *
    * @returns self
-   * @public
    */
-  public timeout(timeout: number): this {
+  public timeout(
+    timeout: number
+  ): Socket<
+    ListenEvents,
+    DecorateAcknowledgements<EmitEvents>,
+    ServerSideEvents,
+    SocketData
+  > {
     this.flags.timeout = timeout;
     return this;
   }
@@ -640,9 +926,25 @@ export class Socket<
   /**
    * Sets up socket middleware.
    *
+   * @example
+   * io.on("connection", (socket) => {
+   *   socket.use(([event, ...args], next) => {
+   *     if (isUnauthorized(event)) {
+   *       return next(new Error("unauthorized event"));
+   *     }
+   *     // do not forget to call next
+   *     next();
+   *   });
+   *
+   *   socket.on("error", (err) => {
+   *     if (err && err.message === "unauthorized event") {
+   *       socket.disconnect();
+   *     }
+   *   });
+   * });
+   *
    * @param {Function} fn - middleware function (event, next)
    * @return {Socket} self
-   * @public
    */
   public use(fn: (event: Event, next: (err?: Error) => void) => void): this {
     this.fns.push(fn);
@@ -685,8 +987,6 @@ export class Socket<
 
   /**
    * A reference to the request that originated the underlying Engine.IO Socket.
-   *
-   * @public
    */
   public get request(): IncomingMessage {
     return this.client.request;
@@ -695,14 +995,30 @@ export class Socket<
   /**
    * A reference to the underlying Client transport connection (Engine.IO Socket object).
    *
-   * @public
+   * @example
+   * io.on("connection", (socket) => {
+   *   console.log(socket.conn.transport.name); // prints "polling" or "websocket"
+   *
+   *   socket.conn.once("upgrade", () => {
+   *     console.log(socket.conn.transport.name); // prints "websocket"
+   *   });
+   * });
    */
   public get conn() {
     return this.client.conn;
   }
 
   /**
-   * @public
+   * Returns the rooms the socket is currently in.
+   *
+   * @example
+   * io.on("connection", (socket) => {
+   *   console.log(socket.rooms); // Set { <socket.id> }
+   *
+   *   socket.join("room1");
+   *
+   *   console.log(socket.rooms); // Set { <socket.id>, "room1" }
+   * });
    */
   public get rooms(): Set<Room> {
     return this.adapter.socketRooms(this.id) || new Set();
@@ -712,8 +1028,14 @@ export class Socket<
    * Adds a listener that will be fired when any event is received. The event name is passed as the first argument to
    * the callback.
    *
+   * @example
+   * io.on("connection", (socket) => {
+   *   socket.onAny((event, ...args) => {
+   *     console.log(`got event ${event}`);
+   *   });
+   * });
+   *
    * @param listener
-   * @public
    */
   public onAny(listener: (...args: any[]) => void): this {
     this._anyListeners = this._anyListeners || [];
@@ -726,7 +1048,6 @@ export class Socket<
    * the callback. The listener is added to the beginning of the listeners array.
    *
    * @param listener
-   * @public
    */
   public prependAny(listener: (...args: any[]) => void): this {
     this._anyListeners = this._anyListeners || [];
@@ -737,8 +1058,22 @@ export class Socket<
   /**
    * Removes the listener that will be fired when any event is received.
    *
+   * @example
+   * io.on("connection", (socket) => {
+   *   const catchAllListener = (event, ...args) => {
+   *     console.log(`got event ${event}`);
+   *   }
+   *
+   *   socket.onAny(catchAllListener);
+   *
+   *   // remove a specific listener
+   *   socket.offAny(catchAllListener);
+   *
+   *   // or remove all listeners
+   *   socket.offAny();
+   * });
+   *
    * @param listener
-   * @public
    */
   public offAny(listener?: (...args: any[]) => void): this {
     if (!this._anyListeners) {
@@ -761,28 +1096,25 @@ export class Socket<
   /**
    * Returns an array of listeners that are listening for any event that is specified. This array can be manipulated,
    * e.g. to remove listeners.
-   *
-   * @public
    */
   public listenersAny() {
     return this._anyListeners || [];
   }
 
   /**
-   * Adds a listener that will be fired when any event is emitted. The event name is passed as the first argument to the
-   * callback.
+   * Adds a listener that will be fired when any event is sent. The event name is passed as the first argument to
+   * the callback.
    *
-   * @param listener
+   * Note: acknowledgements sent to the client are not included.
    *
-   * <pre><code>
-   *
-   * socket.onAnyOutgoing((event, ...args) => {
-   *   console.log(event);
+   * @example
+   * io.on("connection", (socket) => {
+   *   socket.onAnyOutgoing((event, ...args) => {
+   *     console.log(`sent event ${event}`);
+   *   });
    * });
    *
-   * </pre></code>
-   *
-   * @public
+   * @param listener
    */
   public onAnyOutgoing(listener: (...args: any[]) => void): this {
     this._anyOutgoingListeners = this._anyOutgoingListeners || [];
@@ -794,17 +1126,14 @@ export class Socket<
    * Adds a listener that will be fired when any event is emitted. The event name is passed as the first argument to the
    * callback. The listener is added to the beginning of the listeners array.
    *
-   * @param listener
-   *
-   * <pre><code>
-   *
-   * socket.prependAnyOutgoing((event, ...args) => {
-   *   console.log(event);
+   * @example
+   * io.on("connection", (socket) => {
+   *   socket.prependAnyOutgoing((event, ...args) => {
+   *     console.log(`sent event ${event}`);
+   *   });
    * });
    *
-   * </pre></code>
-   *
-   * @public
+   * @param listener
    */
   public prependAnyOutgoing(listener: (...args: any[]) => void): this {
     this._anyOutgoingListeners = this._anyOutgoingListeners || [];
@@ -813,24 +1142,24 @@ export class Socket<
   }
 
   /**
-   * Removes the listener that will be fired when any event is emitted.
+   * Removes the listener that will be fired when any event is sent.
    *
-   * @param listener
+   * @example
+   * io.on("connection", (socket) => {
+   *   const catchAllListener = (event, ...args) => {
+   *     console.log(`sent event ${event}`);
+   *   }
    *
-   * <pre><code>
+   *   socket.onAnyOutgoing(catchAllListener);
    *
-   * const handler = (event, ...args) => {
-   *   console.log(event);
-   * }
+   *   // remove a specific listener
+   *   socket.offAnyOutgoing(catchAllListener);
    *
-   * socket.onAnyOutgoing(handler);
+   *   // or remove all listeners
+   *   socket.offAnyOutgoing();
+   * });
    *
-   * // then later
-   * socket.offAnyOutgoing(handler);
-   *
-   * </pre></code>
-   *
-   * @public
+   * @param listener - the catch-all listener
    */
   public offAnyOutgoing(listener?: (...args: any[]) => void): this {
     if (!this._anyOutgoingListeners) {
@@ -853,8 +1182,6 @@ export class Socket<
   /**
    * Returns an array of listeners that are listening for any event that is specified. This array can be manipulated,
    * e.g. to remove listeners.
-   *
-   * @public
    */
   public listenersAnyOutgoing() {
     return this._anyOutgoingListeners || [];
@@ -876,14 +1203,12 @@ export class Socket<
     }
   }
 
-  private newBroadcastOperator(): BroadcastOperator<EmitEvents, SocketData> {
+  private newBroadcastOperator() {
     const flags = Object.assign({}, this.flags);
     this.flags = {};
-    return new BroadcastOperator(
-      this.adapter,
-      new Set<Room>(),
-      new Set<Room>([this.id]),
-      flags
-    );
+    return new BroadcastOperator<
+      DecorateAcknowledgementsWithMultipleResponses<EmitEvents>,
+      SocketData
+    >(this.adapter, new Set<Room>(), new Set<Room>([this.id]), flags);
   }
 }

lib/typed-events.ts

@@ -178,3 +178,66 @@ export abstract class StrictEventEmitter<
     >[];
   }
 }
+
+export type Last<T extends any[]> = T extends [...infer H, infer L] ? L : any;
+export type AllButLast<T extends any[]> = T extends [...infer H, infer L]
+  ? H
+  : any[];
+export type FirstArg<T> = T extends (arg: infer Param) => infer Result
+  ? Param
+  : any;
+export type SecondArg<T> = T extends (
+  err: Error,
+  arg: infer Param
+) => infer Result
+  ? Param
+  : any;
+
+type PrependTimeoutError<T extends any[]> = {
+  [K in keyof T]: T[K] extends (...args: infer Params) => infer Result
+    ? (err: Error, ...args: Params) => Result
+    : T[K];
+};
+
+type ExpectMultipleResponses<T extends any[]> = {
+  [K in keyof T]: T[K] extends (err: Error, arg: infer Param) => infer Result
+    ? (err: Error, arg: Param[]) => Result
+    : T[K];
+};
+
+/**
+ * Utility type to decorate the acknowledgement callbacks with a timeout error.
+ *
+ * This is needed because the timeout() flag breaks the symmetry between the sender and the receiver:
+ *
+ * @example
+ * interface Events {
+ *   "my-event": (val: string) => void;
+ * }
+ *
+ * socket.on("my-event", (cb) => {
+ *   cb("123"); // one single argument here
+ * });
+ *
+ * socket.timeout(1000).emit("my-event", (err, val) => {
+ *   // two arguments there (the "err" argument is not properly typed)
+ * });
+ *
+ */
+export type DecorateAcknowledgements<E> = {
+  [K in keyof E]: E[K] extends (...args: infer Params) => infer Result
+    ? (...args: PrependTimeoutError<Params>) => Result
+    : E[K];
+};
+
+export type DecorateAcknowledgementsWithTimeoutAndMultipleResponses<E> = {
+  [K in keyof E]: E[K] extends (...args: infer Params) => infer Result
+    ? (...args: ExpectMultipleResponses<PrependTimeoutError<Params>>) => Result
+    : E[K];
+};
+
+export type DecorateAcknowledgementsWithMultipleResponses<E> = {
+  [K in keyof E]: E[K] extends (...args: infer Params) => infer Result
+    ? (...args: ExpectMultipleResponses<Params>) => Result
+    : E[K];
+};

lib/uws.ts

@@ -25,7 +25,9 @@ export function patchAdapter(app /* : TemplatedApp */) {
     if (isNew) {
       socket.conn.on("upgrade", () => {
         const rooms = this.sids.get(id);
-        subscribe(this.nsp.name, socket, isNew, rooms);
+        if (rooms) {
+          subscribe(this.nsp.name, socket, isNew, rooms);
+        }
       });
     }
   };

package.json

@@ -1,6 +1,6 @@
 {
   "name": "socket.io",
-  "version": "4.5.1",
+  "version": "4.6.1",
   "description": "node.js realtime framework server",
   "keywords": [
     "realtime",
@@ -40,7 +40,7 @@
     "compile": "rimraf ./dist && tsc",
     "test": "npm run format:check && npm run compile && npm run test:types && npm run test:unit",
     "test:types": "tsd",
-    "test:unit": "nyc mocha --require ts-node/register --reporter spec --slow 200 --bail --timeout 10000 test/socket.io.ts",
+    "test:unit": "nyc mocha --require ts-node/register --reporter spec --slow 200 --bail --timeout 10000 test/index.ts",
     "format:check": "prettier --check \"lib/**/*.ts\" \"test/**/*.ts\"",
     "format:fix": "prettier --write \"lib/**/*.ts\" \"test/**/*.ts\"",
     "prepack": "npm run compile"
@@ -49,23 +49,23 @@
     "accepts": "~1.3.4",
     "base64id": "~2.0.0",
     "debug": "~4.3.2",
-    "engine.io": "~6.2.0",
-    "socket.io-adapter": "~2.4.0",
-    "socket.io-parser": "~4.0.4"
+    "engine.io": "~6.4.1",
+    "socket.io-adapter": "~2.5.2",
+    "socket.io-parser": "~4.2.1"
   },
   "devDependencies": {
     "@types/mocha": "^9.0.0",
     "expect.js": "0.3.1",
-    "mocha": "^3.5.3",
+    "mocha": "^10.0.0",
     "nyc": "^15.1.0",
     "prettier": "^2.3.2",
     "rimraf": "^3.0.2",
-    "socket.io-client": "4.5.1",
+    "socket.io-client": "4.6.1",
     "socket.io-client-v2": "npm:socket.io-client@^2.4.0",
-    "superagent": "^6.1.0",
+    "superagent": "^8.0.0",
     "supertest": "^6.1.6",
     "ts-node": "^10.2.1",
-    "tsd": "^0.17.0",
+    "tsd": "^0.21.0",
     "typescript": "^4.4.2",
     "uWebSockets.js": "github:uNetworking/uWebSockets.js#v20.0.0"
   },

test/close.ts

@@ -0,0 +1,148 @@
+import { createServer } from "http";
+import { io as ioc } from "socket.io-client";
+import { join } from "path";
+import { exec } from "child_process";
+import { Server } from "..";
+import expect from "expect.js";
+import {
+  createClient,
+  eioHandshake,
+  eioPoll,
+  eioPush,
+  getPort,
+} from "./support/util";
+
+describe("close", () => {
+  it("should be able to close sio sending a srv", (done) => {
+    const httpServer = createServer().listen(0);
+    const io = new Server(httpServer);
+    const port = getPort(io);
+    const net = require("net");
+    const server = net.createServer();
+
+    const clientSocket = createClient(io, "/", { reconnection: false });
+
+    clientSocket.on("disconnect", () => {
+      expect(io.sockets.sockets.size).to.equal(0);
+      server.listen(port);
+    });
+
+    clientSocket.on("connect", () => {
+      expect(io.sockets.sockets.size).to.equal(1);
+      io.close();
+    });
+
+    server.once("listening", () => {
+      // PORT should be free
+      server.close((error) => {
+        expect(error).to.be(undefined);
+        done();
+      });
+    });
+  });
+
+  it("should be able to close sio sending a srv", (done) => {
+    const io = new Server(0);
+    const port = getPort(io);
+    const net = require("net");
+    const server = net.createServer();
+
+    const clientSocket = ioc("ws://0.0.0.0:" + port, {
+      reconnection: false,
+    });
+
+    clientSocket.on("disconnect", () => {
+      expect(io.sockets.sockets.size).to.equal(0);
+      server.listen(port);
+    });
+
+    clientSocket.on("connect", () => {
+      expect(io.sockets.sockets.size).to.equal(1);
+      io.close();
+    });
+
+    server.once("listening", () => {
+      // PORT should be free
+      server.close((error) => {
+        expect(error).to.be(undefined);
+        done();
+      });
+    });
+  });
+
+  describe("graceful close", () => {
+    function fixture(filename) {
+      return (
+        '"' +
+        process.execPath +
+        '" "' +
+        join(__dirname, "fixtures", filename) +
+        '"'
+      );
+    }
+
+    it("should stop socket and timers", (done) => {
+      exec(fixture("server-close.ts"), done);
+    });
+  });
+
+  describe("protocol violations", () => {
+    it("should close the connection when receiving several CONNECT packets", async () => {
+      const httpServer = createServer();
+      const io = new Server(httpServer);
+
+      httpServer.listen(0);
+
+      const sid = await eioHandshake(httpServer);
+      // send a first CONNECT packet
+      await eioPush(httpServer, sid, "40");
+      // send another CONNECT packet
+      await eioPush(httpServer, sid, "40");
+      // session is cleanly closed (not discarded, see 'client.close()')
+      // first, we receive the Socket.IO handshake response
+      await eioPoll(httpServer, sid);
+      // then a close packet
+      const body = await eioPoll(httpServer, sid);
+      expect(body).to.be("6\u001e1");
+
+      io.close();
+    });
+
+    it("should close the connection when receiving an EVENT packet while not connected", async () => {
+      const httpServer = createServer();
+      const io = new Server(httpServer);
+
+      httpServer.listen(0);
+
+      const sid = await eioHandshake(httpServer);
+      // send an EVENT packet
+      await eioPush(httpServer, sid, '42["some event"]');
+      // session is cleanly closed, we receive a close packet
+      const body = await eioPoll(httpServer, sid);
+      expect(body).to.be("6\u001e1");
+
+      io.close();
+    });
+
+    it("should close the connection when receiving an invalid packet", async () => {
+      const httpServer = createServer();
+      const io = new Server(httpServer);
+
+      httpServer.listen(0);
+
+      const sid = await eioHandshake(httpServer);
+      // send a CONNECT packet
+      await eioPush(httpServer, sid, "40");
+      // send an invalid packet
+      await eioPush(httpServer, sid, "4abc");
+      // session is cleanly closed (not discarded, see 'client.close()')
+      // first, we receive the Socket.IO handshake response
+      await eioPoll(httpServer, sid);
+      // then a close packet
+      const body = await eioPoll(httpServer, sid);
+      expect(body).to.be("6\u001e1");
+
+      io.close();
+    });
+  });
+});

test/connection-state-recovery.ts

@@ -0,0 +1,247 @@
+import { Server, Socket } from "..";
+import expect from "expect.js";
+import { waitFor, eioHandshake, eioPush, eioPoll } from "./support/util";
+import { createServer, Server as HttpServer } from "http";
+import { Adapter } from "socket.io-adapter";
+
+async function init(httpServer: HttpServer, io: Server) {
+  // Engine.IO handshake
+  const sid = await eioHandshake(httpServer);
+
+  // Socket.IO handshake
+  await eioPush(httpServer, sid, "40");
+  const handshakeBody = await eioPoll(httpServer, sid);
+
+  expect(handshakeBody.startsWith("40")).to.be(true);
+
+  const handshake = JSON.parse(handshakeBody.substring(2));
+
+  expect(handshake.sid).to.not.be(undefined);
+  // in that case, the handshake also contains a private session ID
+  expect(handshake.pid).to.not.be(undefined);
+
+  io.emit("hello");
+
+  const message = await eioPoll(httpServer, sid);
+
+  expect(message.startsWith('42["hello"')).to.be(true);
+
+  const offset = JSON.parse(message.substring(2))[1];
+  // in that case, each packet also includes an offset in the data array
+  expect(offset).to.not.be(undefined);
+
+  await eioPush(httpServer, sid, "1");
+
+  return [handshake.sid, handshake.pid, offset];
+}
+
+describe("connection state recovery", () => {
+  it("should restore session and missed packets", async () => {
+    const httpServer = createServer().listen(0);
+    const io = new Server(httpServer, {
+      connectionStateRecovery: {},
+    });
+
+    let serverSocket;
+
+    io.once("connection", (socket) => {
+      socket.join("room1");
+      serverSocket = socket;
+    });
+
+    const [sid, pid, offset] = await init(httpServer, io);
+
+    io.emit("hello1"); // broadcast
+    io.to("room1").emit("hello2"); // broadcast to room
+    serverSocket.emit("hello3"); // direct message
+
+    const newSid = await eioHandshake(httpServer);
+    await eioPush(
+      httpServer,
+      newSid,
+      `40{"pid":"${pid}","offset":"${offset}"}`
+    );
+
+    const payload = await eioPoll(httpServer, newSid);
+    const packets = payload.split("\x1e");
+
+    expect(packets.length).to.eql(4);
+
+    // note: EVENT packets are received before the CONNECT packet, which is a bit weird
+    // see also: https://github.com/socketio/socket.io-deno/commit/518f534e1c205b746b1cb21fe76b187dabc96f34
+    expect(packets[0].startsWith('42["hello1"')).to.be(true);
+    expect(packets[1].startsWith('42["hello2"')).to.be(true);
+    expect(packets[2].startsWith('42["hello3"')).to.be(true);
+    expect(packets[3]).to.eql(`40{"sid":"${sid}","pid":"${pid}"}`);
+
+    io.close();
+  });
+
+  it("should restore rooms and data attributes", async () => {
+    const httpServer = createServer().listen(0);
+    const io = new Server(httpServer, {
+      connectionStateRecovery: {},
+    });
+
+    io.once("connection", (socket) => {
+      expect(socket.recovered).to.eql(false);
+
+      socket.join("room1");
+      socket.join("room2");
+      socket.data.foo = "bar";
+    });
+
+    const [sid, pid, offset] = await init(httpServer, io);
+
+    const newSid = await eioHandshake(httpServer);
+
+    const [socket] = await Promise.all([
+      waitFor<Socket>(io, "connection"),
+      eioPush(httpServer, newSid, `40{"pid":"${pid}","offset":"${offset}"}`),
+    ]);
+
+    expect(socket.id).to.eql(sid);
+    expect(socket.recovered).to.eql(true);
+
+    expect(socket.rooms.has(socket.id)).to.eql(true);
+    expect(socket.rooms.has("room1")).to.eql(true);
+    expect(socket.rooms.has("room2")).to.eql(true);
+
+    expect(socket.data.foo).to.eql("bar");
+
+    await eioPoll(httpServer, newSid); // drain buffer
+    io.close();
+  });
+
+  it("should not run middlewares upon recovery by default", async () => {
+    const httpServer = createServer().listen(0);
+    const io = new Server(httpServer, {
+      connectionStateRecovery: {},
+    });
+
+    const [_, pid, offset] = await init(httpServer, io);
+
+    io.use((socket, next) => {
+      socket.data.middlewareWasCalled = true;
+
+      next();
+    });
+
+    const newSid = await eioHandshake(httpServer);
+
+    const [socket] = await Promise.all([
+      waitFor<Socket>(io, "connection"),
+      eioPush(httpServer, newSid, `40{"pid":"${pid}","offset":"${offset}"}`),
+    ]);
+
+    expect(socket.recovered).to.be(true);
+    expect(socket.data.middlewareWasCalled).to.be(undefined);
+
+    await eioPoll(httpServer, newSid); // drain buffer
+    io.close();
+  });
+
+  it("should run middlewares even upon recovery", async () => {
+    const httpServer = createServer().listen(0);
+    const io = new Server(httpServer, {
+      connectionStateRecovery: {
+        skipMiddlewares: false,
+      },
+    });
+
+    const [_, pid, offset] = await init(httpServer, io);
+
+    io.use((socket, next) => {
+      socket.data.middlewareWasCalled = true;
+
+      next();
+    });
+
+    const newSid = await eioHandshake(httpServer);
+
+    const [socket] = await Promise.all([
+      waitFor<Socket>(io, "connection"),
+      eioPush(httpServer, newSid, `40{"pid":"${pid}","offset":"${offset}"}`),
+    ]);
+
+    expect(socket.recovered).to.be(true);
+    expect(socket.data.middlewareWasCalled).to.be(true);
+
+    await eioPoll(httpServer, newSid); // drain buffer
+    io.close();
+  });
+
+  it("should fail to restore an unknown session", async () => {
+    const httpServer = createServer().listen(0);
+    const io = new Server(httpServer, {
+      connectionStateRecovery: {},
+    });
+
+    // Engine.IO handshake
+    const sid = await eioHandshake(httpServer);
+
+    // Socket.IO handshake
+    await eioPush(httpServer, sid, '40{"pid":"foo","offset":"bar"}');
+
+    const handshakeBody = await eioPoll(httpServer, sid);
+
+    expect(handshakeBody.startsWith("40")).to.be(true);
+
+    const handshake = JSON.parse(handshakeBody.substring(2));
+
+    expect(handshake.sid).to.not.eql("foo");
+    expect(handshake.pid).to.not.eql("bar");
+
+    io.close();
+  });
+
+  it("should be disabled by default", async () => {
+    const httpServer = createServer().listen(0);
+    const io = new Server(httpServer);
+
+    // Engine.IO handshake
+    const sid = await eioHandshake(httpServer);
+
+    // Socket.IO handshake
+    await eioPush(httpServer, sid, "40");
+
+    const handshakeBody = await eioPoll(httpServer, sid);
+
+    expect(handshakeBody.startsWith("40")).to.be(true);
+
+    const handshake = JSON.parse(handshakeBody.substring(2));
+
+    expect(handshake.sid).to.not.be(undefined);
+    expect(handshake.pid).to.be(undefined);
+
+    io.close();
+  });
+
+  it("should not call adapter#persistSession or adapter#restoreSession if disabled", async () => {
+    const httpServer = createServer().listen(0);
+
+    class DummyAdapter extends Adapter {
+      override persistSession(session) {
+        expect.fail();
+      }
+
+      override restoreSession(pid, offset) {
+        expect.fail();
+        return Promise.reject("should not happen");
+      }
+    }
+
+    const io = new Server(httpServer, {
+      adapter: DummyAdapter,
+    });
+
+    // Engine.IO handshake
+    const sid = await eioHandshake(httpServer);
+
+    await eioPush(httpServer, sid, '40{"pid":"foo","offset":"bar"}');
+    await eioPoll(httpServer, sid);
+    await eioPush(httpServer, sid, "1");
+
+    io.close();
+  });
+});

test/handshake.ts

@@ -0,0 +1,87 @@
+import { Server } from "..";
+import expect from "expect.js";
+import { getPort, success } from "./support/util";
+
+describe("handshake", () => {
+  const request = require("superagent");
+
+  it("should send the Access-Control-Allow-xxx headers on OPTIONS request", (done) => {
+    const io = new Server(0, {
+      cors: {
+        origin: "http://localhost:54023",
+        methods: ["GET", "POST"],
+        allowedHeaders: ["content-type"],
+        credentials: true,
+      },
+    });
+    request
+      .options(`http://localhost:${getPort(io)}/socket.io/default/`)
+      .query({ transport: "polling", EIO: 4 })
+      .set("Origin", "http://localhost:54023")
+      .end((err, res) => {
+        expect(res.status).to.be(204);
+
+        expect(res.headers["access-control-allow-origin"]).to.be(
+          "http://localhost:54023"
+        );
+        expect(res.headers["access-control-allow-methods"]).to.be("GET,POST");
+        expect(res.headers["access-control-allow-headers"]).to.be(
+          "content-type"
+        );
+        expect(res.headers["access-control-allow-credentials"]).to.be("true");
+        success(done, io);
+      });
+  });
+
+  it("should send the Access-Control-Allow-xxx headers on GET request", (done) => {
+    const io = new Server(0, {
+      cors: {
+        origin: "http://localhost:54024",
+        methods: ["GET", "POST"],
+        allowedHeaders: ["content-type"],
+        credentials: true,
+      },
+    });
+    request
+      .get(`http://localhost:${getPort(io)}/socket.io/default/`)
+      .query({ transport: "polling", EIO: 4 })
+      .set("Origin", "http://localhost:54024")
+      .end((err, res) => {
+        expect(res.status).to.be(200);
+
+        expect(res.headers["access-control-allow-origin"]).to.be(
+          "http://localhost:54024"
+        );
+        expect(res.headers["access-control-allow-credentials"]).to.be("true");
+        success(done, io);
+      });
+  });
+
+  it("should allow request if custom function in opts.allowRequest returns true", (done) => {
+    const io = new Server(0, {
+      allowRequest: (req, callback) => callback(null, true),
+    });
+
+    request
+      .get(`http://localhost:${getPort(io)}/socket.io/default/`)
+      .query({ transport: "polling", EIO: 4 })
+      .end((err, res) => {
+        expect(res.status).to.be(200);
+        success(done, io);
+      });
+  });
+
+  it("should disallow request if custom function in opts.allowRequest returns false", (done) => {
+    const io = new Server(0, {
+      allowRequest: (req, callback) => callback(null, false),
+    });
+    request
+      .get(`http://localhost:${getPort(io)}/socket.io/default/`)
+      .set("origin", "http://foo.example")
+      .query({ transport: "polling", EIO: 4 })
+      .end((err, res) => {
+        expect(res.status).to.be(403);
+        success(done, io);
+      });
+  });
+});

test/index.ts

@@ -0,0 +1,24 @@
+"use strict";
+
+import expect from "expect.js";
+
+describe("socket.io", () => {
+  it("should be the same version as client", () => {
+    const version = require("../package").version;
+    expect(version).to.be(require("socket.io-client/package.json").version);
+  });
+
+  require("./server-attachment");
+  require("./handshake");
+  require("./close");
+  require("./namespaces");
+  require("./socket");
+  require("./messaging-many");
+  require("./middleware");
+  require("./socket-middleware");
+  require("./v2-compatibility");
+  require("./socket-timeout");
+  require("./uws");
+  require("./utility-methods");
+  require("./connection-state-recovery");
+});

test/messaging-many.ts

@@ -0,0 +1,587 @@
+import { Server } from "..";
+import expect from "expect.js";
+import {
+  createClient,
+  createPartialDone,
+  success,
+  successFn,
+  waitFor,
+} from "./support/util";
+
+describe("messaging many", () => {
+  it("emits to a namespace", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+    const socket3 = createClient(io, "/test");
+
+    const partialDone = createPartialDone(
+      2,
+      successFn(done, io, socket1, socket2, socket3)
+    );
+
+    socket1.on("a", (a) => {
+      expect(a).to.be("b");
+      partialDone();
+    });
+    socket2.on("a", (a) => {
+      expect(a).to.be("b");
+      partialDone();
+    });
+    socket3.on("a", () => {
+      done(new Error("not"));
+    });
+
+    let sockets = 3;
+    io.on("connection", () => {
+      --sockets || emit();
+    });
+    io.of("/test", () => {
+      --sockets || emit();
+    });
+
+    function emit() {
+      io.emit("a", "b");
+    }
+  });
+
+  it("emits binary data to a namespace", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+    const socket3 = createClient(io, "/test");
+
+    const partialDone = createPartialDone(
+      2,
+      successFn(done, io, socket1, socket2, socket3)
+    );
+
+    socket1.on("bin", (a) => {
+      expect(Buffer.isBuffer(a)).to.be(true);
+      partialDone();
+    });
+    socket2.on("bin", (a) => {
+      expect(Buffer.isBuffer(a)).to.be(true);
+      partialDone();
+    });
+    socket3.on("bin", () => {
+      done(new Error("not"));
+    });
+
+    let sockets = 3;
+    io.on("connection", () => {
+      --sockets || emit();
+    });
+    io.of("/test", () => {
+      --sockets || emit();
+    });
+
+    function emit() {
+      io.emit("bin", Buffer.alloc(10));
+    }
+  });
+
+  it("emits to the rest", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+    const socket3 = createClient(io, "/test");
+
+    socket1.on("a", (a) => {
+      expect(a).to.be("b");
+      socket1.emit("finish");
+    });
+    socket2.emit("broadcast");
+    socket2.on("a", () => {
+      done(new Error("done"));
+    });
+    socket3.on("a", () => {
+      done(new Error("not"));
+    });
+
+    io.on("connection", (socket) => {
+      socket.on("broadcast", () => {
+        socket.broadcast.emit("a", "b");
+      });
+      socket.on("finish", () => {
+        success(done, io, socket1, socket2, socket3);
+      });
+    });
+  });
+
+  it("emits to rooms", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+
+    socket2.on("a", () => {
+      done(new Error("not"));
+    });
+    socket1.on("a", () => {
+      success(done, io, socket1, socket2);
+    });
+    socket1.emit("join", "woot");
+    socket1.emit("emit", "woot");
+
+    io.on("connection", (socket) => {
+      socket.on("join", (room, fn) => {
+        socket.join(room);
+        fn && fn();
+      });
+
+      socket.on("emit", (room) => {
+        io.in(room).emit("a");
+      });
+    });
+  });
+
+  it("emits to rooms avoiding dupes", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+
+    const partialDone = createPartialDone(
+      2,
+      successFn(done, io, socket1, socket2)
+    );
+
+    socket2.on("a", () => {
+      done(new Error("not"));
+    });
+    socket1.on("a", partialDone);
+    socket2.on("b", partialDone);
+
+    socket1.emit("join", "woot");
+    socket1.emit("join", "test");
+    socket2.emit("join", "third", () => {
+      socket2.emit("emit");
+    });
+
+    io.on("connection", (socket) => {
+      socket.on("join", (room, fn) => {
+        socket.join(room);
+        fn && fn();
+      });
+
+      socket.on("emit", () => {
+        io.in("woot").in("test").emit("a");
+        io.in("third").emit("b");
+      });
+    });
+  });
+
+  it("broadcasts to rooms", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+    const socket3 = createClient(io, "/", { multiplex: false });
+
+    const partialDone = createPartialDone(
+      2,
+      successFn(done, io, socket1, socket2, socket3)
+    );
+
+    socket1.emit("join", "woot");
+    socket2.emit("join", "test");
+    socket3.emit("join", "test", () => {
+      socket3.emit("broadcast");
+    });
+
+    socket1.on("a", () => {
+      done(new Error("not"));
+    });
+    socket2.on("a", () => {
+      partialDone();
+    });
+    socket3.on("a", () => {
+      done(new Error("not"));
+    });
+    socket3.on("b", () => {
+      partialDone();
+    });
+
+    io.on("connection", (socket) => {
+      socket.on("join", (room, fn) => {
+        socket.join(room);
+        fn && fn();
+      });
+
+      socket.on("broadcast", () => {
+        socket.broadcast.to("test").emit("a");
+        socket.emit("b");
+      });
+    });
+  });
+
+  it("broadcasts binary data to rooms", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+    const socket3 = createClient(io, "/", { multiplex: false });
+
+    const partialDone = createPartialDone(
+      2,
+      successFn(done, io, socket1, socket2, socket3)
+    );
+
+    socket1.emit("join", "woot");
+    socket2.emit("join", "test");
+    socket3.emit("join", "test", () => {
+      socket3.emit("broadcast");
+    });
+
+    socket1.on("bin", (data) => {
+      throw new Error("got bin in socket1");
+    });
+    socket2.on("bin", (data) => {
+      expect(Buffer.isBuffer(data)).to.be(true);
+      partialDone();
+    });
+    socket2.on("bin2", (data) => {
+      throw new Error("socket2 got bin2");
+    });
+    socket3.on("bin", (data) => {
+      throw new Error("socket3 got bin");
+    });
+    socket3.on("bin2", (data) => {
+      expect(Buffer.isBuffer(data)).to.be(true);
+      partialDone();
+    });
+
+    io.on("connection", (socket) => {
+      socket.on("join", (room, fn) => {
+        socket.join(room);
+        fn && fn();
+      });
+      socket.on("broadcast", () => {
+        socket.broadcast.to("test").emit("bin", Buffer.alloc(5));
+        socket.emit("bin2", Buffer.alloc(5));
+      });
+    });
+  });
+
+  it("keeps track of rooms", (done) => {
+    const io = new Server(0);
+    const socket = createClient(io);
+
+    io.on("connection", (s) => {
+      s.join("a");
+      expect(s.rooms).to.contain(s.id, "a");
+      s.join("b");
+      expect(s.rooms).to.contain(s.id, "a", "b");
+      s.join("c");
+      expect(s.rooms).to.contain(s.id, "a", "b", "c");
+      s.leave("b");
+      expect(s.rooms).to.contain(s.id, "a", "c");
+      (s as any).leaveAll();
+      expect(s.rooms.size).to.eql(0);
+
+      success(done, io, socket);
+    });
+  });
+
+  it("deletes empty rooms", (done) => {
+    const io = new Server(0);
+    const socket = createClient(io);
+
+    io.on("connection", (s) => {
+      s.join("a");
+      expect(s.nsp.adapter.rooms).to.contain("a");
+      s.leave("a");
+      expect(s.nsp.adapter.rooms).to.not.contain("a");
+
+      success(done, io, socket);
+    });
+  });
+
+  it("should properly cleanup left rooms", (done) => {
+    const io = new Server(0);
+    const socket = createClient(io);
+
+    io.on("connection", (s) => {
+      s.join("a");
+      expect(s.rooms).to.contain(s.id, "a");
+      s.join("b");
+      expect(s.rooms).to.contain(s.id, "a", "b");
+      s.leave("unknown");
+      expect(s.rooms).to.contain(s.id, "a", "b");
+      (s as any).leaveAll();
+      expect(s.rooms.size).to.eql(0);
+
+      success(done, io, socket);
+    });
+  });
+
+  it("allows to join several rooms at once", (done) => {
+    const io = new Server(0);
+    const socket = createClient(io);
+
+    io.on("connection", (s) => {
+      s.join(["a", "b", "c"]);
+      expect(s.rooms).to.contain(s.id, "a", "b", "c");
+      success(done, io, socket);
+    });
+  });
+
+  it("should exclude specific sockets when broadcasting", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+    const socket3 = createClient(io, "/", { multiplex: false });
+
+    socket2.on("a", () => {
+      done(new Error("not"));
+    });
+    socket3.on("a", () => {
+      done(new Error("not"));
+    });
+    socket1.on("a", successFn(done, io, socket1, socket2, socket3));
+
+    io.on("connection", (socket) => {
+      socket.on("exclude", (id) => {
+        socket.broadcast.except(id).emit("a");
+      });
+    });
+
+    socket2.on("connect", () => {
+      socket3.emit("exclude", socket2.id);
+    });
+  });
+
+  it("should exclude a specific room when broadcasting", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+    const socket3 = createClient(io, "/", { multiplex: false });
+
+    socket2.on("a", () => {
+      done(new Error("not"));
+    });
+    socket3.on("a", () => {
+      done(new Error("not"));
+    });
+    socket1.on("a", successFn(done, io, socket1, socket2, socket3));
+
+    io.on("connection", (socket) => {
+      socket.on("join", (room, cb) => {
+        socket.join(room);
+        cb();
+      });
+      socket.on("broadcast", () => {
+        socket.broadcast.except("room1").emit("a");
+      });
+    });
+
+    socket2.emit("join", "room1", () => {
+      socket3.emit("broadcast");
+    });
+  });
+
+  it("should return an immutable broadcast operator", (done) => {
+    const io = new Server(0);
+    const clientSocket = createClient(io);
+
+    io.on("connection", (socket) => {
+      const operator = socket.local
+        .compress(false)
+        .to(["room1", "room2"])
+        .except("room3");
+      operator.compress(true).emit("hello");
+      operator.volatile.emit("hello");
+      operator.to("room4").emit("hello");
+      operator.except("room5").emit("hello");
+      socket.emit("hello");
+      socket.to("room6").emit("hello");
+      // @ts-ignore
+      expect(operator.rooms).to.contain("room1", "room2");
+      // @ts-ignore
+      expect(operator.rooms).to.not.contain("room4", "room5", "room6");
+      // @ts-ignore
+      expect(operator.exceptRooms).to.contain("room3");
+      // @ts-ignore
+      expect(operator.flags).to.eql({ local: true, compress: false });
+
+      success(done, io, clientSocket);
+    });
+  });
+
+  it("should broadcast and expect multiple acknowledgements", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+    const socket3 = createClient(io, "/", { multiplex: false });
+
+    socket1.on("some event", (cb) => {
+      cb(1);
+    });
+
+    socket2.on("some event", (cb) => {
+      cb(2);
+    });
+
+    socket3.on("some event", (cb) => {
+      cb(3);
+    });
+
+    Promise.all([
+      waitFor(socket1, "connect"),
+      waitFor(socket2, "connect"),
+      waitFor(socket3, "connect"),
+    ]).then(() => {
+      io.timeout(2000).emit("some event", (err, responses) => {
+        expect(err).to.be(null);
+        expect(responses).to.have.length(3);
+        expect(responses).to.contain(1, 2, 3);
+
+        success(done, io, socket1, socket2, socket3);
+      });
+    });
+  });
+
+  it("should fail when a client does not acknowledge the event in the given delay", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+    const socket3 = createClient(io, "/", { multiplex: false });
+
+    socket1.on("some event", (cb) => {
+      cb(1);
+    });
+
+    socket2.on("some event", (cb) => {
+      cb(2);
+    });
+
+    socket3.on("some event", () => {
+      // timeout
+    });
+
+    Promise.all([
+      waitFor(socket1, "connect"),
+      waitFor(socket2, "connect"),
+      waitFor(socket3, "connect"),
+    ]).then(() => {
+      io.timeout(200).emit("some event", (err, responses) => {
+        expect(err).to.be.an(Error);
+        expect(responses).to.have.length(2);
+        expect(responses).to.contain(1, 2);
+
+        success(done, io, socket1, socket2, socket3);
+      });
+    });
+  });
+
+  it("should broadcast and expect multiple acknowledgements (promise)", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+    const socket3 = createClient(io, "/", { multiplex: false });
+
+    socket1.on("some event", (cb) => {
+      cb(1);
+    });
+
+    socket2.on("some event", (cb) => {
+      cb(2);
+    });
+
+    socket3.on("some event", (cb) => {
+      cb(3);
+    });
+
+    Promise.all([
+      waitFor(socket1, "connect"),
+      waitFor(socket2, "connect"),
+      waitFor(socket3, "connect"),
+    ]).then(async () => {
+      const responses = await io.timeout(2000).emitWithAck("some event");
+      expect(responses).to.contain(1, 2, 3);
+
+      success(done, io, socket1, socket2, socket3);
+    });
+  });
+
+  it("should fail when a client does not acknowledge the event in the given delay (promise)", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+    const socket3 = createClient(io, "/", { multiplex: false });
+
+    socket1.on("some event", (cb) => {
+      cb(1);
+    });
+
+    socket2.on("some event", (cb) => {
+      cb(2);
+    });
+
+    socket3.on("some event", () => {
+      // timeout
+    });
+
+    Promise.all([
+      waitFor(socket1, "connect"),
+      waitFor(socket2, "connect"),
+      waitFor(socket3, "connect"),
+    ]).then(async () => {
+      try {
+        await io.timeout(200).emitWithAck("some event");
+        expect.fail();
+      } catch (err) {
+        expect(err).to.be.an(Error);
+        // @ts-ignore
+        expect(err.responses).to.have.length(2);
+        // @ts-ignore
+        expect(err.responses).to.contain(1, 2);
+
+        success(done, io, socket1, socket2, socket3);
+      }
+    });
+  });
+
+  it("should broadcast and return if the packet is sent to 0 client", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/", { multiplex: false });
+    const socket2 = createClient(io, "/", { multiplex: false });
+    const socket3 = createClient(io, "/", { multiplex: false });
+
+    socket1.on("some event", () => {
+      done(new Error("should not happen"));
+    });
+
+    socket2.on("some event", () => {
+      done(new Error("should not happen"));
+    });
+
+    socket3.on("some event", () => {
+      done(new Error("should not happen"));
+    });
+
+    io.to("room123")
+      .timeout(200)
+      .emit("some event", (err, responses) => {
+        expect(err).to.be(null);
+        expect(responses).to.have.length(0);
+
+        success(done, io, socket1, socket2, socket3);
+      });
+  });
+
+  it("should precompute the WebSocket frame when broadcasting", (done) => {
+    const io = new Server(0);
+    const socket = createClient(io, "/chat", {
+      transports: ["websocket"],
+    });
+    const partialDone = createPartialDone(2, successFn(done, io, socket));
+
+    io.of("/chat").on("connection", (s) => {
+      s.conn.once("packetCreate", (packet) => {
+        expect(packet.options.wsPreEncodedFrame).to.be.an(Array);
+        partialDone();
+      });
+      io.of("/chat").compress(false).emit("woot", "hi");
+    });
+
+    socket.on("woot", partialDone);
+  });
+});

test/middleware.ts

@@ -0,0 +1,210 @@
+import { Server, Socket } from "..";
+import expect from "expect.js";
+import {
+  success,
+  createClient,
+  successFn,
+  createPartialDone,
+} from "./support/util";
+
+describe("middleware", () => {
+  it("should call functions", (done) => {
+    const io = new Server(0);
+
+    let run = 0;
+    io.use((socket, next) => {
+      expect(socket).to.be.a(Socket);
+      run++;
+      next();
+    });
+    io.use((socket, next) => {
+      expect(socket).to.be.a(Socket);
+      run++;
+      next();
+    });
+
+    const socket = createClient(io);
+    socket.on("connect", () => {
+      expect(run).to.be(2);
+
+      success(done, io, socket);
+    });
+  });
+
+  it("should pass errors", (done) => {
+    const io = new Server(0);
+
+    io.use((socket, next) => {
+      next(new Error("Authentication error"));
+    });
+    io.use((socket, next) => {
+      done(new Error("nope"));
+    });
+
+    const socket = createClient(io);
+    socket.on("connect", () => {
+      done(new Error("nope"));
+    });
+    socket.on("connect_error", (err) => {
+      expect(err.message).to.be("Authentication error");
+
+      success(done, io, socket);
+    });
+  });
+
+  it("should pass an object", (done) => {
+    const io = new Server(0);
+
+    io.use((socket, next) => {
+      const err = new Error("Authentication error");
+      // @ts-ignore
+      err.data = { a: "b", c: 3 };
+      next(err);
+    });
+
+    const socket = createClient(io);
+    socket.on("connect", () => {
+      done(new Error("nope"));
+    });
+    socket.on("connect_error", (err) => {
+      expect(err).to.be.an(Error);
+      expect(err.message).to.eql("Authentication error");
+      // @ts-ignore
+      expect(err.data).to.eql({ a: "b", c: 3 });
+
+      success(done, io, socket);
+    });
+  });
+
+  it("should only call connection after fns", (done) => {
+    const io = new Server(0);
+
+    io.use((socket: any, next) => {
+      socket.name = "guillermo";
+      next();
+    });
+
+    const clientSocket = createClient(io);
+    io.on("connection", (socket) => {
+      expect((socket as any).name).to.be("guillermo");
+
+      success(done, io, clientSocket);
+    });
+  });
+
+  it("should only call connection after (lengthy) fns", (done) => {
+    const io = new Server(0);
+
+    let authenticated = false;
+
+    io.use((socket, next) => {
+      setTimeout(() => {
+        authenticated = true;
+        next();
+      }, 300);
+    });
+
+    const socket = createClient(io);
+    socket.on("connect", () => {
+      expect(authenticated).to.be(true);
+
+      success(done, io, socket);
+    });
+  });
+
+  it("should be ignored if socket gets closed", (done) => {
+    const io = new Server(0);
+
+    let socket;
+    io.use((s, next) => {
+      socket.io.engine.close();
+      s.client.conn.on("close", () => {
+        process.nextTick(next);
+        setTimeout(() => {
+          success(done, io, socket);
+        }, 50);
+      });
+    });
+
+    socket = createClient(io);
+    io.on("connection", (socket) => {
+      done(new Error("should not fire"));
+    });
+  });
+
+  it("should call functions in expected order", (done) => {
+    const io = new Server(0);
+
+    const result: number[] = [];
+
+    io.use(() => {
+      done(new Error("should not fire"));
+    });
+    io.of("/chat").use((socket, next) => {
+      result.push(1);
+      setTimeout(next, 50);
+    });
+    io.of("/chat").use((socket, next) => {
+      result.push(2);
+      setTimeout(next, 50);
+    });
+    io.of("/chat").use((socket, next) => {
+      result.push(3);
+      setTimeout(next, 50);
+    });
+
+    const chat = createClient(io, "/chat");
+    chat.on("connect", () => {
+      expect(result).to.eql([1, 2, 3]);
+
+      success(done, io, chat);
+    });
+  });
+
+  it("should disable the merge of handshake packets", (done) => {
+    const io = new Server(0);
+
+    io.use((socket, next) => {
+      next();
+    });
+
+    const socket = createClient(io);
+    socket.on("connect", successFn(done, io, socket));
+  });
+
+  it("should work with a custom namespace", (done) => {
+    const io = new Server(0);
+    const socket1 = createClient(io, "/");
+    const socket2 = createClient(io, "/chat");
+
+    const partialDone = createPartialDone(
+      2,
+      successFn(done, io, socket1, socket2)
+    );
+
+    io.of("/chat").use((socket, next) => {
+      next();
+    });
+
+    socket1.on("connect", partialDone);
+    socket2.on("connect", partialDone);
+  });
+
+  it("should only set `connected` to true after the middleware execution", (done) => {
+    const io = new Server(0);
+    const clientSocket = createClient(io, "/");
+
+    io.use((socket, next) => {
+      expect(socket.connected).to.be(false);
+      expect(socket.disconnected).to.be(true);
+      next();
+    });
+
+    io.on("connection", (socket) => {
+      expect(socket.connected).to.be(true);
+      expect(socket.disconnected).to.be(false);
+
+      success(done, io, clientSocket);
+    });
+  });
+});

test/namespaces.ts

@@ -0,0 +1,667 @@
+import type { SocketId } from "socket.io-adapter";
+import { Server, Namespace, Socket } from "..";
+import expect from "expect.js";
+import {
+  success,
+  createClient,
+  successFn,
+  createPartialDone,
+} from "./support/util";
+
+describe("namespaces", () => {
+  it("should be accessible through .sockets", () => {
+    const io = new Server();
+    expect(io.sockets).to.be.a(Namespace);
+  });
+
+  it("should be aliased", () => {
+    const io = new Server();
+    expect(io.use).to.be.a("function");
+    expect(io.to).to.be.a("function");
+    expect(io["in"]).to.be.a("function");
+    expect(io.emit).to.be.a("function");
+    expect(io.send).to.be.a("function");
+    expect(io.write).to.be.a("function");
+    expect(io.allSockets).to.be.a("function");
+    expect(io.compress).to.be.a("function");
+  });
+
+  it("should return an immutable broadcast operator", () => {
+    const io = new Server();
+    const operator = io.local.to(["room1", "room2"]).except("room3");
+    operator.compress(true).emit("hello");
+    operator.volatile.emit("hello");
+    operator.to("room4").emit("hello");
+    operator.except("room5").emit("hello");
+    io.to("room6").emit("hello");
+    // @ts-ignore
+    expect(operator.rooms).to.contain("room1", "room2");
+    // @ts-ignore
+    expect(operator.exceptRooms).to.contain("room3");
+    // @ts-ignore
+    expect(operator.flags).to.eql({ local: true });
+  });
+
+  it("should automatically connect", (done) => {
+    const io = new Server(0);
+    const socket = createClient(io);
+    socket.on("connect", successFn(done, io, socket));
+  });
+
+  it("should fire a `connection` event", (done) => {
+    const io = new Server(0);
+    const clientSocket = createClient(io);
+
+    io.on("connection", (socket) => {
+      expect(socket).to.be.a(Socket);
+      success(done, io, clientSocket);
+    });
+  });
+
+  it("should fire a `connect` event", (done) => {
+    const io = new Server(0);
+    const clientSocket = createClient(io);
+
+    io.on("connect", (socket) => {
+      expect(socket).to.be.a(Socket);
+      success(done, io, clientSocket);
+    });
+  });
+
+  it("should work with many sockets", (done) => {
+    const io = new Server(0);
+    io.of("/chat");
+    io.of("/news");
+    const chat = createClient(io, "/chat");
+    const news = createClient(io, "/news");
+
+    let total = 2;
+    chat.on("connect", () => {
+      --total || success(done, io, chat, news);
+    });
+    news.on("connect", () => {
+      --total || success(done, io, chat, news);
+    });
+  });
+
+  it('should be able to equivalently start with "" or "/" on server', (done) => {
+    const io = new Server(0);
+    const c1 = createClient(io, "/");
+    const c2 = createClient(io, "/abc");
+
+    let total = 2;
+    io.of("").on("connection", () => {
+      --total || success(done, io, c1, c2);
+    });
+    io.of("abc").on("connection", () => {
+      --total || success(done, io, c1, c2);
+    });
+  });
+
+  it('should be equivalent for "" and "/" on client', (done) => {
+    const io = new Server(0);
+    const c1 = createClient(io, "");
+
+    io.of("/").on("connection", successFn(done, io, c1));
+  });
+
+  it("should work with `of` and many sockets", (done) => {
+    const io = new Server(0);
+    const chat = createClient(io, "/chat");
+    const news = createClient(io, "/news");
+
+    let total = 2;
+    io.of("/news").on("connection", (socket) => {
+      expect(socket).to.be.a(Socket);
+      --total || success(done, io, chat, news);
+    });
+    io.of("/news").on("connection", (socket) => {
+      expect(socket).to.be.a(Socket);
+      --total || success(done, io, chat, news);
+    });
+  });
+
+  it("should work with `of` second param", (done) => {
+    const io = new Server(0);
+    const chat = createClient(io, "/chat");
+    const news = createClient(io, "/news");
+
+    let total = 2;
+    io.of("/news", (socket) => {
+      expect(socket).to.be.a(Socket);
+      --total || success(done, io, chat, news);
+    });
+    io.of("/news", (socket) => {
+      expect(socket).to.be.a(Socket);
+      --total || success(done, io, chat, news);
+    });
+  });
+
+  it("should disconnect upon transport disconnection", (done) => {
+    const io = new Server(0);
+    const chat = createClient(io, "/chat");
+    const news = createClient(io, "/news");
+
+    let total = 2;
+    let totald = 2;
+    let s;
+    io.of("/news", (socket) => {
+      socket.on("disconnect", (reason) => {
+        --totald || success(done, io, chat, news);
+      });
+      --total || close();
+    });
+    io.of("/chat", (socket) => {
+      s = socket;
+      socket.on("disconnect", (reason) => {
+        --totald || success(done, io, chat, news);
+      });
+      --total || close();
+    });
+    function close() {
+      s.disconnect(true);
+    }
+  });
+
+  it("should fire a `disconnecting` event just before leaving all rooms", (done) => {
+    const io = new Server(0);
+    const socket = createClient(io);
+
+    io.on("connection", (s) => {
+      s.join("a");
+      // FIXME not sure why process.nextTick() is needed here
+      process.nextTick(() => s.disconnect());
+
+      let total = 2;
+      s.on("disconnecting", (reason) => {
+        expect(s.rooms).to.contain(s.id, "a");
+        total--;
+      });
+
+      s.on("disconnect", (reason) => {
+        expect(s.rooms.size).to.eql(0);
+        --total || success(done, io, socket);
+      });
+    });
+  });
+
+  it("should return error connecting to non-existent namespace", (done) => {
+    const io = new Server(0);
+    const socket = createClient(io, "/doesnotexist");
+
+    socket.on("connect_error", (err) => {
+      expect(err.message).to.be("Invalid namespace");
+      success(done, io);
+    });
+  });
+
+  it("should not reuse same-namespace connections", (done) => {
+    const io = new Server(0);
+    const clientSocket1 = createClient(io);
+    const clientSocket2 = createClient(io);
+
+    let connections = 0;
+    io.on("connection", () => {
+      connections++;
+      if (connections === 2) {
+        success(done, io, clientSocket1, clientSocket2);
+      }
+    });
+  });
+
+  it("should find all clients in a namespace", (done) => {
+    const io = new Server(0);
+    const chatSids: string[] = [];
+    let otherSid: SocketId | null = null;
+
+    const c1 = createClient(io, "/chat");
+    const c2 = createClient(io, "/chat", { forceNew: true });
+    const c3 = createClient(io, "/other", { forceNew: true });
+
+    let total = 3;
+    io.of("/chat").on("connection", (socket) => {
+      chatSids.push(socket.id);
+      --total || getSockets();
+    });
+    io.of("/other").on("connection", (socket) => {
+      otherSid = socket.id;
+      --total || getSockets();
+    });
+
+    async function getSockets() {
+      const sids = await io.of("/chat").allSockets();
+
+      expect(sids).to.contain(chatSids[0], chatSids[1]);
+      expect(sids).to.not.contain(otherSid);
+      success(done, io, c1, c2, c3);
+    }
+  });
+
+  it("should find all clients in a namespace room", (done) => {
+    const io = new Server(0);
+    let chatFooSid: SocketId | null = null;
+    let chatBarSid: SocketId | null = null;
+    let otherSid: SocketId | null = null;
+
+    const c1 = createClient(io, "/chat");
+    const c2 = createClient(io, "/chat", { forceNew: true });
+    const c3 = createClient(io, "/other", { forceNew: true });
+
+    let chatIndex = 0;
+    let total = 3;
+    io.of("/chat").on("connection", (socket) => {
+      if (chatIndex++) {
+        socket.join("foo");
+        chatFooSid = socket.id;
+        --total || getSockets();
+      } else {
+        socket.join("bar");
+        chatBarSid = socket.id;
+        --total || getSockets();
+      }
+    });
+    io.of("/other").on("connection", (socket) => {
+      socket.join("foo");
+      otherSid = socket.id;
+      --total || getSockets();
+    });
+
+    async function getSockets() {
+      const sids = await io.of("/chat").in("foo").allSockets();
+
+      expect(sids).to.contain(chatFooSid);
+      expect(sids).to.not.contain(chatBarSid);
+      expect(sids).to.not.contain(otherSid);
+      success(done, io, c1, c2, c3);
+    }
+  });
+
+  it("should find all clients across namespace rooms", (done) => {
+    const io = new Server(0);
+    let chatFooSid: SocketId | null = null;
+    let chatBarSid: SocketId | null = null;
+    let otherSid: SocketId | null = null;
+
+    const c1 = createClient(io, "/chat");
+    const c2 = createClient(io, "/chat", { forceNew: true });
+    const c3 = createClient(io, "/other", { forceNew: true });
+
+    let chatIndex = 0;
+    let total = 3;
+    io.of("/chat").on("connection", (socket) => {
+      if (chatIndex++) {
+        socket.join("foo");
+        chatFooSid = socket.id;
+        --total || getSockets();
+      } else {
+        socket.join("bar");
+        chatBarSid = socket.id;
+        --total || getSockets();
+      }
+    });
+    io.of("/other").on("connection", (socket) => {
+      socket.join("foo");
+      otherSid = socket.id;
+      --total || getSockets();
+    });
+
+    async function getSockets() {
+      const sids = await io.of("/chat").allSockets();
+      expect(sids).to.contain(chatFooSid, chatBarSid);
+      expect(sids).to.not.contain(otherSid);
+      success(done, io, c1, c2, c3);
+    }
+  });
+
+  it("should not emit volatile event after regular event", (done) => {
+    const io = new Server(0);
+
+    let counter = 0;
+    io.of("/chat").on("connection", (s) => {
+      // Wait to make sure there are no packets being sent for opening the connection
+      setTimeout(() => {
+        io.of("/chat").emit("ev", "data");
+        io.of("/chat").volatile.emit("ev", "data");
+      }, 50);
+    });
+
+    const socket = createClient(io, "/chat");
+    socket.on("ev", () => {
+      counter++;
+    });
+
+    setTimeout(() => {
+      expect(counter).to.be(1);
+      success(done, io, socket);
+    }, 500);
+  });
+
+  it("should emit volatile event", (done) => {
+    const io = new Server(0);
+
+    let counter = 0;
+    io.of("/chat").on("connection", (s) => {
+      // Wait to make sure there are no packets being sent for opening the connection
+      setTimeout(() => {
+        io.of("/chat").volatile.emit("ev", "data");
+      }, 100);
+    });
+
+    const socket = createClient(io, "/chat");
+    socket.on("ev", () => {
+      counter++;
+    });
+
+    setTimeout(() => {
+      expect(counter).to.be(1);
+      success(done, io, socket);
+    }, 500);
+  });
+
+  it("should enable compression by default", (done) => {
+    const io = new Server(0);
+    const socket = createClient(io, "/chat");
+
+    io.of("/chat").on("connection", (s) => {
+      s.conn.once("packetCreate", (packet) => {
+        expect(packet.options.compress).to.be(true);
+        success(done, io, socket);
+      });
+      io.of("/chat").emit("woot", "hi");
+    });
+  });
+
+  it("should disable compression", (done) => {
+    const io = new Server(0);
+    const socket = createClient(io, "/chat");
+
+    io.of("/chat").on("connection", (s) => {
+      s.conn.once("packetCreate", (packet) => {
+        expect(packet.options.compress).to.be(false);
+        success(done, io, socket);
+      });
+      io.of("/chat").compress(false).emit("woot", "hi");
+    });
+  });
+
+  it("should throw on reserved event", () => {
+    const io = new Server();
+
+    expect(() => io.emit("connect")).to.throwException(
+      /"connect" is a reserved event name/
+    );
+  });
+
+  it("should close a client without namespace", (done) => {
+    const io = new Server(0, {
+      connectTimeout: 10,
+    });
+
+    const socket = createClient(io);
+
+    // @ts-ignore
+    socket.io.engine.write = () => {}; // prevent the client from sending a CONNECT packet
+
+    socket.on("disconnect", successFn(done, io, socket));
+  });
+
+  it("should exclude a specific socket when emitting", (done) => {
+    const io = new Server(0);
+
+    const socket1 = createClient(io, "/");
+    const socket2 = createClient(io, "/");
+
+    socket2.on("a", () => {
+      done(new Error("should not happen"));
+    });
+    socket1.on("a", successFn(done, io, socket1, socket2));
+
+    socket2.on("connect", () => {
+      io.except(socket2.id).emit("a");
+    });
+  });
+
+  it("should exclude a specific socket when emitting (in a namespace)", (done) => {
+    const io = new Server(0);
+
+    const nsp = io.of("/nsp");
+
+    const socket1 = createClient(io, "/nsp");
+    const socket2 = createClient(io, "/nsp");
+
+    socket2.on("a", () => {
+      done(new Error("not"));
+    });
+    socket1.on("a", successFn(done, io, socket1, socket2));
+
+    socket2.on("connect", () => {
+      nsp.except(socket2.id).emit("a");
+    });
+  });
+
+  it("should exclude a specific room when emitting", (done) => {
+    const io = new Server(0);
+
+    const nsp = io.of("/nsp");
+
+    const socket1 = createClient(io, "/nsp");
+    const socket2 = createClient(io, "/nsp");
+
+    socket1.on("a", successFn(done, io, socket1, socket2));
+    socket2.on("a", () => {
+      done(new Error("not"));
+    });
+
+    nsp.on("connection", (socket) => {
+      socket.on("broadcast", () => {
+        socket.join("room1");
+        nsp.except("room1").emit("a");
+      });
+    });
+
+    socket2.emit("broadcast");
+  });
+
+  it("should emit an 'new_namespace' event", (done) => {
+    const io = new Server();
+
+    io.on("new_namespace", (namespace) => {
+      expect(namespace.name).to.eql("/nsp");
+      done();
+    });
+
+    io.of("/nsp");
+  });
+
+  it("should not clean up a non-dynamic namespace", (done) => {
+    const io = new Server(0, { cleanupEmptyChildNamespaces: true });
+    const c1 = createClient(io, "/chat");
+
+    c1.on("connect", () => {
+      c1.disconnect();
+
+      // Give it some time to disconnect the client
+      setTimeout(() => {
+        expect(io._nsps.has("/chat")).to.be(true);
+        expect(io._nsps.get("/chat")!.sockets.size).to.be(0);
+        success(done, io);
+      }, 100);
+    });
+
+    io.of("/chat");
+  });
+
+  describe("dynamic namespaces", () => {
+    it("should allow connections to dynamic namespaces with a regex", (done) => {
+      const io = new Server(0);
+      const socket = createClient(io, "/dynamic-101");
+      const partialDone = createPartialDone(4, successFn(done, io, socket));
+
+      let dynamicNsp = io
+        .of(/^\/dynamic-\d+$/)
+        .on("connect", (socket) => {
+          expect(socket.nsp.name).to.be("/dynamic-101");
+          dynamicNsp.emit("hello", 1, "2", { 3: "4" });
+          partialDone();
+        })
+        .use((socket, next) => {
+          next();
+          partialDone();
+        });
+      socket.on("connect_error", (err) => {
+        expect().fail();
+      });
+      socket.on("connect", () => {
+        partialDone();
+      });
+      socket.on("hello", (a, b, c) => {
+        expect(a).to.eql(1);
+        expect(b).to.eql("2");
+        expect(c).to.eql({ 3: "4" });
+        partialDone();
+      });
+    });
+
+    it("should allow connections to dynamic namespaces with a function", (done) => {
+      const io = new Server(0);
+      const socket = createClient(io, "/dynamic-101");
+
+      io.of((name, query, next) => next(null, "/dynamic-101" === name));
+      socket.on("connect", successFn(done, io, socket));
+    });
+
+    it("should disallow connections when no dynamic namespace matches", (done) => {
+      const io = new Server(0);
+      const socket = createClient(io, "/abc");
+      io.of(/^\/dynamic-\d+$/);
+      io.of((name, query, next) => next(null, "/dynamic-101" === name));
+
+      socket.on("connect_error", (err) => {
+        expect(err.message).to.be("Invalid namespace");
+        success(done, io, socket);
+      });
+    });
+
+    it("should emit an 'new_namespace' event for a dynamic namespace", (done) => {
+      const io = new Server(0);
+      io.of(/^\/dynamic-\d+$/);
+      const socket = createClient(io, "/dynamic-101");
+
+      io.on("new_namespace", (namespace) => {
+        expect(namespace.name).to.be("/dynamic-101");
+
+        success(done, io, socket);
+      });
+    });
+
+    it("should handle race conditions with dynamic namespaces (#4136)", (done) => {
+      const io = new Server(0);
+      const counters = {
+        connected: 0,
+        created: 0,
+        events: 0,
+      };
+      const buffer: Function[] = [];
+      io.on("new_namespace", (namespace) => {
+        counters.created++;
+      });
+
+      const handler = () => {
+        if (++counters.events === 2) {
+          expect(counters.created).to.equal(1);
+          success(done, io, one, two);
+        }
+      };
+
+      io.of((name, query, next) => {
+        buffer.push(next);
+        if (buffer.length === 2) {
+          buffer.forEach((next) => next(null, true));
+        }
+      }).on("connection", (socket) => {
+        if (++counters.connected === 2) {
+          io.of("/dynamic-101").emit("message");
+        }
+      });
+
+      let one = createClient(io, "/dynamic-101");
+      let two = createClient(io, "/dynamic-101");
+      one.on("message", handler);
+      two.on("message", handler);
+    });
+
+    it("should clean up namespace when cleanupEmptyChildNamespaces is on and there are no more sockets in a namespace", (done) => {
+      const io = new Server(0, { cleanupEmptyChildNamespaces: true });
+      const c1 = createClient(io, "/dynamic-101");
+
+      c1.on("connect", () => {
+        c1.disconnect();
+
+        // Give it some time to disconnect and clean up the namespace
+        setTimeout(() => {
+          expect(io._nsps.has("/dynamic-101")).to.be(false);
+          success(done, io);
+        }, 100);
+      });
+
+      io.of(/^\/dynamic-\d+$/);
+    });
+
+    it("should allow a client to connect to a cleaned up namespace", (done) => {
+      const io = new Server(0, { cleanupEmptyChildNamespaces: true });
+      const c1 = createClient(io, "/dynamic-101");
+
+      c1.on("connect", () => {
+        c1.disconnect();
+
+        // Give it some time to disconnect and clean up the namespace
+        setTimeout(() => {
+          expect(io._nsps.has("/dynamic-101")).to.be(false);
+
+          const c2 = createClient(io, "/dynamic-101");
+
+          c2.on("connect", () => {
+            success(done, io, c2);
+          });
+
+          c2.on("connect_error", () => {
+            done(
+              new Error("Client got error when connecting to dynamic namespace")
+            );
+          });
+        }, 100);
+      });
+
+      io.of(/^\/dynamic-\d+$/);
+    });
+
+    it("should not clean up namespace when cleanupEmptyChildNamespaces is off and there are no more sockets in a namespace", (done) => {
+      const io = new Server(0);
+      const c1 = createClient(io, "/dynamic-101");
+
+      c1.on("connect", () => {
+        c1.disconnect();
+
+        // Give it some time to disconnect and clean up the namespace
+        setTimeout(() => {
+          expect(io._nsps.has("/dynamic-101")).to.be(true);
+          expect(io._nsps.get("/dynamic-101")!.sockets.size).to.be(0);
+          success(done, io);
+        }, 100);
+      });
+
+      io.of(/^\/dynamic-\d+$/);
+    });
+
+    it("should attach a child namespace to its parent upon manual creation", () => {
+      const io = new Server(0);
+      const parentNamespace = io.of(/^\/dynamic-\d+$/);
+      const childNamespace = io.of("/dynamic-101");
+
+      // @ts-ignore
+      expect(parentNamespace.children.has(childNamespace)).to.be(true);
+
+      io.close();
+    });
+  });
+});

test/server-attachment.ts

@@ -0,0 +1,174 @@
+import { Server } from "..";
+import { createServer } from "http";
+import request from "supertest";
+import expect from "expect.js";
+import { getPort, successFn } from "./support/util";
+
+describe("server attachment", () => {
+  describe("http.Server", () => {
+    const clientVersion = require("socket.io-client/package.json").version;
+
+    const testSource = (filename) => (done) => {
+      const srv = createServer();
+      new Server(srv);
+      request(srv)
+        .get("/socket.io/" + filename)
+        .buffer(true)
+        .end((err, res) => {
+          if (err) return done(err);
+          expect(res.headers["content-type"]).to.be(
+            "application/javascript; charset=utf-8"
+          );
+          expect(res.headers.etag).to.be('"' + clientVersion + '"');
+          expect(res.headers["x-sourcemap"]).to.be(undefined);
+          expect(res.text).to.match(/engine\.io/);
+          expect(res.status).to.be(200);
+          done();
+        });
+    };
+
+    const testSourceMap = (filename) => (done) => {
+      const srv = createServer();
+      new Server(srv);
+      request(srv)
+        .get("/socket.io/" + filename)
+        .buffer(true)
+        .end((err, res) => {
+          if (err) return done(err);
+          expect(res.headers["content-type"]).to.be(
+            "application/json; charset=utf-8"
+          );
+          expect(res.headers.etag).to.be('"' + clientVersion + '"');
+          expect(res.text).to.match(/engine\.io/);
+          expect(res.status).to.be(200);
+          done();
+        });
+    };
+
+    it("should serve client", testSource("socket.io.js"));
+    it(
+      "should serve client with query string",
+      testSource("socket.io.js?buster=" + Date.now())
+    );
+    it("should serve source map", testSourceMap("socket.io.js.map"));
+    it("should serve client (min)", testSource("socket.io.min.js"));
+
+    it("should serve source map (min)", testSourceMap("socket.io.min.js.map"));
+
+    it("should serve client (gzip)", (done) => {
+      const srv = createServer();
+      new Server(srv);
+      request(srv)
+        .get("/socket.io/socket.io.js")
+        .set("accept-encoding", "gzip,br,deflate")
+        .buffer(true)
+        .end((err, res) => {
+          if (err) return done(err);
+          expect(res.headers["content-encoding"]).to.be("gzip");
+          expect(res.status).to.be(200);
+          done();
+        });
+    });
+
+    it(
+      "should serve bundle with msgpack parser",
+      testSource("socket.io.msgpack.min.js")
+    );
+
+    it(
+      "should serve source map for bundle with msgpack parser",
+      testSourceMap("socket.io.msgpack.min.js.map")
+    );
+
+    it("should serve the ESM bundle", testSource("socket.io.esm.min.js"));
+
+    it(
+      "should serve the source map for the ESM bundle",
+      testSourceMap("socket.io.esm.min.js.map")
+    );
+
+    it("should handle 304", (done) => {
+      const srv = createServer();
+      new Server(srv);
+      request(srv)
+        .get("/socket.io/socket.io.js")
+        .set("If-None-Match", '"' + clientVersion + '"')
+        .end((err, res) => {
+          if (err) return done(err);
+          expect(res.statusCode).to.be(304);
+          done();
+        });
+    });
+
+    it("should handle 304", (done) => {
+      const srv = createServer();
+      new Server(srv);
+      request(srv)
+        .get("/socket.io/socket.io.js")
+        .set("If-None-Match", 'W/"' + clientVersion + '"')
+        .end((err, res) => {
+          if (err) return done(err);
+          expect(res.statusCode).to.be(304);
+          done();
+        });
+    });
+
+    it("should not serve static files", (done) => {
+      const srv = createServer();
+      new Server(srv, { serveClient: false });
+      request(srv).get("/socket.io/socket.io.js").expect(400, done);
+    });
+
+    it("should work with #attach", (done) => {
+      const srv = createServer((req, res) => {
+        res.writeHead(404);
+        res.end();
+      });
+      const sockets = new Server();
+      sockets.attach(srv);
+      request(srv)
+        .get("/socket.io/socket.io.js")
+        .end((err, res) => {
+          if (err) return done(err);
+          expect(res.status).to.be(200);
+          done();
+        });
+    });
+
+    it("should work with #attach (and merge options)", () => {
+      const srv = createServer((req, res) => {
+        res.writeHead(404);
+        res.end();
+      });
+      const server = new Server({
+        pingTimeout: 6000,
+      });
+      server.attach(srv, {
+        pingInterval: 24000,
+      });
+      // @ts-ignore
+      expect(server.eio.opts.pingTimeout).to.eql(6000);
+      // @ts-ignore
+      expect(server.eio.opts.pingInterval).to.eql(24000);
+      server.close();
+    });
+  });
+
+  describe("port", () => {
+    it("should be bound", (done) => {
+      const io = new Server(0);
+
+      request(`http://localhost:${getPort(io)}`)
+        .get("/socket.io/socket.io.js")
+        .expect(200, successFn(done, io));
+    });
+
+    it("with listen", (done) => {
+      const io = new Server().listen(0);
+
+      request(`http://localhost:${getPort(io)}`)
+        .get("/socket.io/socket.io.js")
+        .expect(200, successFn(done, io));
+    });
+  });
+});

test/socket-middleware.ts

@@ -0,0 +1,60 @@
+import { Server } from "..";
+import expect from "expect.js";
+import { success, createClient } from "./support/util";
+
+describe("socket middleware", () => {
+  it("should call functions", (done) => {
+    const io = new Server(0);
+    const clientSocket = createClient(io, "/", { multiplex: false });
+
+    clientSocket.emit("join", "woot");
+
+    let run = 0;
+
+    io.on("connection", (socket) => {
+      socket.use((event, next) => {
+        expect(event).to.eql(["join", "woot"]);
+        event.unshift("wrap");
+        run++;
+        next();
+      });
+      socket.use((event, next) => {
+        expect(event).to.eql(["wrap", "join", "woot"]);
+        run++;
+        next();
+      });
+      socket.on("wrap", (data1, data2) => {
+        expect(data1).to.be("join");
+        expect(data2).to.be("woot");
+        expect(run).to.be(2);
+
+        success(done, io, clientSocket);
+      });
+    });
+  });
+
+  it("should pass errors", (done) => {
+    const io = new Server(0);
+    const clientSocket = createClient(io, "/", { multiplex: false });
+
+    clientSocket.emit("join", "woot");
+
+    io.on("connection", (socket) => {
+      socket.use((event, next) => {
+        next(new Error("Authentication error"));
+      });
+      socket.use((event, next) => {
+        done(new Error("should not happen"));
+      });
+      socket.on("join", () => {
+        done(new Error("should not happen"));
+      });
+      socket.on("error", (err) => {
+        expect(err).to.be.an(Error);
+        expect(err.message).to.eql("Authentication error");
+
+        success(done, io, clientSocket);
+      });
+    });
+  });
+});

test/socket-timeout.ts

@@ -54,4 +54,34 @@ describe("timeout", () => {
       });
     });
   });
+
+  it("should timeout if the client does not acknowledge the event (promise)", (done) => {
+    const io = new Server(0);
+    const client = createClient(io, "/");
+
+    io.on("connection", async (socket) => {
+      try {
+        await socket.timeout(50).emitWithAck("unknown");
+        expect.fail();
+      } catch (err) {
+        expect(err).to.be.an(Error);
+        success(done, io, client);
+      }
+    });
+  });
+
+  it("should not timeout if the client does acknowledge the event (promise)", (done) => {
+    const io = new Server(0);
+    const client = createClient(io, "/");
+
+    client.on("echo", (arg, cb) => {
+      cb(arg);
+    });
+
+    io.on("connection", async (socket) => {
+      const value = await socket.timeout(50).emitWithAck("echo", 42);
+      expect(value).to.be(42);
+      success(done, io, client);
+    });
+  });
 });

test/socket.io.test-d.ts

@@ -4,6 +4,7 @@ import type { DefaultEventsMap } from "../lib/typed-events";
 import { createServer } from "http";
 import { expectError, expectType } from "tsd";
 import { Adapter } from "socket.io-adapter";
+import type { DisconnectReason } from "../lib/socket";
 
 // This file is run by tsd, not mocha.
 
@@ -17,10 +18,10 @@ describe("server", () => {
           sio.on("connection", (s) => {
             expectType<Socket<DefaultEventsMap, DefaultEventsMap>>(s);
             s.on("disconnect", (reason) => {
-              expectType<string>(reason);
+              expectType<DisconnectReason>(reason);
             });
             s.on("disconnecting", (reason) => {
-              expectType<string>(reason);
+              expectType<DisconnectReason>(reason);
             });
           });
           sio.on("connect", (s) => {
@@ -91,6 +92,28 @@ describe("server", () => {
         });
       });
     });
+
+    describe("emitWithAck", () => {
+      it("accepts any parameters", () => {
+        const srv = createServer();
+        const sio = new Server(srv);
+        srv.listen(async () => {
+          const value = await sio
+            .timeout(1000)
+            .emitWithAck("ackFromServerSingleArg", true, "123");
+          expectType<any>(value);
+
+          sio.on("connection", async (s) => {
+            const value1 = await s.emitWithAck(
+              "ackFromServerSingleArg",
+              true,
+              "123"
+            );
+            expectType<any>(value1);
+          });
+        });
+      });
+    });
   });
 
   describe("single event map", () => {
@@ -166,10 +189,32 @@ describe("server", () => {
   describe("listen and emit event maps", () => {
     interface ClientToServerEvents {
       helloFromClient: (message: string) => void;
+      ackFromClient: (
+        a: string,
+        b: number,
+        ack: (c: string, d: number) => void
+      ) => void;
     }
 
     interface ServerToClientEvents {
       helloFromServer: (message: string, x: number) => void;
+      ackFromServer: (
+        a: boolean,
+        b: string,
+        ack: (c: boolean, d: string) => void
+      ) => void;
+
+      ackFromServerSingleArg: (
+        a: boolean,
+        b: string,
+        ack: (c: string) => void
+      ) => void;
+
+      multipleAckFromServer: (
+        a: boolean,
+        b: string,
+        ack: (c: string) => void
+      ) => void;
     }
 
     describe("on", () => {
@@ -184,6 +229,13 @@ describe("server", () => {
               expectType<string>(message);
               done();
             });
+
+            s.on("ackFromClient", (a, b, cb) => {
+              expectType<string>(a);
+              expectType<number>(b);
+              expectType<(c: string, d: number) => void>(cb);
+              cb("123", 456);
+            });
           });
         });
       });
@@ -208,8 +260,45 @@ describe("server", () => {
         const srv = createServer();
         const sio = new Server<ClientToServerEvents, ServerToClientEvents>(srv);
         srv.listen(() => {
+          sio.emit("helloFromServer", "hi", 1);
+          sio.to("room").emit("helloFromServer", "hi", 1);
+          sio.timeout(1000).emit("helloFromServer", "hi", 1);
+
+          sio
+            .timeout(1000)
+            .emit("multipleAckFromServer", true, "123", (err, c) => {
+              expectType<Error>(err);
+              expectType<string[]>(c);
+            });
+
           sio.on("connection", (s) => {
             s.emit("helloFromServer", "hi", 10);
+
+            s.emit("ackFromServer", true, "123", (c, d) => {
+              expectType<boolean>(c);
+              expectType<string>(d);
+            });
+
+            s.timeout(1000).emit("ackFromServer", true, "123", (err, c, d) => {
+              expectType<Error>(err);
+              expectType<boolean>(c);
+              expectType<string>(d);
+            });
+
+            s.timeout(1000)
+              .to("room")
+              .emit("multipleAckFromServer", true, "123", (err, c) => {
+                expectType<Error>(err);
+                expectType<string[]>(c);
+              });
+
+            s.to("room")
+              .timeout(1000)
+              .emit("multipleAckFromServer", true, "123", (err, c) => {
+                expectType<Error>(err);
+                expectType<string[]>(c);
+              });
+
             done();
           });
         });
@@ -219,6 +308,10 @@ describe("server", () => {
         const srv = createServer();
         const sio = new Server<ClientToServerEvents, ServerToClientEvents>(srv);
         srv.listen(() => {
+          expectError(sio.emit("helloFromClient"));
+          expectError(sio.to("room").emit("helloFromClient"));
+          expectError(sio.timeout(1000).to("room").emit("helloFromClient"));
+
           sio.on("connection", (s) => {
             expectError(s.emit("helloFromClient", "hi"));
             expectError(s.emit("helloFromServer", "hi", 10, "10"));
@@ -231,9 +324,45 @@ describe("server", () => {
         });
       });
     });
+
+    describe("emitWithAck", () => {
+      it("accepts arguments of the correct types", (done) => {
+        const srv = createServer();
+        const sio = new Server<ClientToServerEvents, ServerToClientEvents>(srv);
+        srv.listen(async () => {
+          const value = await sio
+            .timeout(1000)
+            .emitWithAck("multipleAckFromServer", true, "123");
+          expectType<string[]>(value);
+
+          sio.on("connection", async (s) => {
+            const value1 = await s
+              .timeout(1000)
+              .to("room")
+              .emitWithAck("multipleAckFromServer", true, "123");
+            expectType<string[]>(value1);
+
+            const value2 = await s
+              .to("room")
+              .timeout(1000)
+              .emitWithAck("multipleAckFromServer", true, "123");
+            expectType<string[]>(value2);
+
+            const value3 = await s.emitWithAck(
+              "ackFromServerSingleArg",
+              true,
+              "123"
+            );
+            expectType<string>(value3);
+
+            done();
+          });
+        });
+      });
+    });
   });
 
-  describe("listen and emit event maps", () => {
+  describe("listen and emit event maps for the serverSideEmit method", () => {
     interface ClientToServerEvents {
       helloFromClient: (message: string) => void;
     }
@@ -244,6 +373,7 @@ describe("server", () => {
 
     interface InterServerEvents {
       helloFromServerToServer: (message: string, x: number) => void;
+      ackFromServerToServer: (foo: string, cb: (bar: number) => void) => void;
     }
 
     describe("on", () => {
@@ -258,7 +388,7 @@ describe("server", () => {
         expectType<
           Server<ClientToServerEvents, ServerToClientEvents, InterServerEvents>
         >(sio);
-        srv.listen(() => {
+        srv.listen(async () => {
           sio.serverSideEmit("helloFromServerToServer", "hello", 10);
           sio
             .of("/test")
@@ -272,6 +402,22 @@ describe("server", () => {
             expectType<string>(message);
             expectType<number>(x);
           });
+
+          sio.serverSideEmit("ackFromServerToServer", "foo", (err, bar) => {
+            expectType<Error>(err);
+            expectType<number[]>(bar);
+          });
+
+          const value = await sio.serverSideEmitWithAck(
+            "ackFromServerToServer",
+            "foo"
+          );
+          expectType<number[]>(value);
+
+          sio.on("ackFromServerToServer", (foo, cb) => {
+            expectType<string>(foo);
+            expectType<(bar: number) => void>(cb);
+          });
         });
       });
     });

test/support/util.ts

@@ -5,6 +5,7 @@ import {
   Socket as ClientSocket,
   SocketOptions,
 } from "socket.io-client";
+import request from "supertest";
 
 const expect = require("expect.js");
 const i = expect.stringify;
@@ -31,16 +32,88 @@ expect.Assertion.prototype.contain = function (...args) {
 
 export function createClient(
   io: Server,
-  nsp: string,
-  opts?: ManagerOptions & SocketOptions
+  nsp: string = "/",
+  opts?: Partial<ManagerOptions & SocketOptions>
 ): ClientSocket {
   // @ts-ignore
   const port = io.httpServer.address().port;
   return ioc(`http://localhost:${port}${nsp}`, opts);
 }
 
-export function success(done: Function, io: Server, client: ClientSocket) {
+export function success(
+  done: Function,
+  io: Server,
+  ...clients: ClientSocket[]
+) {
   io.close();
-  client.disconnect();
+  clients.forEach((client) => client.disconnect());
   done();
 }
+
+export function successFn(
+  done: () => void,
+  sio: Server,
+  ...clientSockets: ClientSocket[]
+) {
+  return () => success(done, sio, ...clientSockets);
+}
+
+export function getPort(io: Server): number {
+  // @ts-ignore
+  return io.httpServer.address().port;
+}
+
+export function createPartialDone(count: number, done: (err?: Error) => void) {
+  let i = 0;
+  return () => {
+    if (++i === count) {
+      done();
+    } else if (i > count) {
+      done(new Error(`partialDone() called too many times: ${i} > ${count}`));
+    }
+  };
+}
+
+export function waitFor<T = unknown>(emitter, event) {
+  return new Promise<T>((resolve) => {
+    emitter.once(event, resolve);
+  });
+}
+
+// TODO: update superagent as latest release now supports promises
+export function eioHandshake(httpServer): Promise<string> {
+  return new Promise((resolve) => {
+    request(httpServer)
+      .get("/socket.io/")
+      .query({ transport: "polling", EIO: 4 })
+      .end((err, res) => {
+        const sid = JSON.parse(res.text.substring(1)).sid;
+        resolve(sid);
+      });
+  });
+}
+
+export function eioPush(httpServer, sid: string, body: string): Promise<void> {
+  return new Promise((resolve) => {
+    request(httpServer)
+      .post("/socket.io/")
+      .send(body)
+      .query({ transport: "polling", EIO: 4, sid })
+      .expect(200)
+      .end(() => {
+        resolve();
+      });
+  });
+}
+
+export function eioPoll(httpServer, sid): Promise<string> {
+  return new Promise((resolve) => {
+    request(httpServer)
+      .get("/socket.io/")
+      .query({ transport: "polling", EIO: 4, sid })
+      .expect(200)
+      .end((err, res) => {
+        resolve(res.text);
+      });
+  });
+}

test/utility-methods.ts

@@ -6,26 +6,10 @@ import expect from "expect.js";
 import type { AddressInfo } from "net";
 
 import "./support/util";
+import { createPartialDone } from "./support/util";
 
 const SOCKETS_COUNT = 3;
 
-const createPartialDone = (
-  count: number,
-  done: () => void,
-  callback?: () => void
-) => {
-  let i = 0;
-  return () => {
-    i++;
-    if (i === count) {
-      done();
-      if (callback) {
-        callback();
-      }
-    }
-  };
-};
-
 class DummyAdapter extends Adapter {
   fetchSockets(opts: BroadcastOptions): Promise<any[]> {
     return Promise.resolve([
@@ -49,7 +33,7 @@ class DummyAdapter extends Adapter {
   }
 }
 
-describe("socket.io", () => {
+describe("utility methods", () => {
   let io: Server, clientSockets: ClientSocket[], serverSockets: Socket[];
   beforeEach((done) => {
     const srv = createServer();
@@ -59,7 +43,12 @@ describe("socket.io", () => {
 
       clientSockets = [];
       for (let i = 0; i < SOCKETS_COUNT; i++) {
-        clientSockets.push(ioc(`http://localhost:${port}`));
+        clientSockets.push(
+          ioc(`http://localhost:${port}`, {
+            // FIXME needed so that clients are properly closed
+            transports: ["websocket"],
+          })
+        );
       }
 
       serverSockets = [];
@@ -77,100 +66,99 @@ describe("socket.io", () => {
     clientSockets.forEach((socket) => socket.disconnect());
   });
 
-  describe("utility methods", () => {
-    describe("fetchSockets", () => {
-      it("returns all socket instances", async () => {
-        const sockets = await io.fetchSockets();
-        expect(sockets.length).to.eql(3);
-      });
+  describe("fetchSockets", () => {
+    it("returns all socket instances", async () => {
+      const sockets = await io.fetchSockets();
+      expect(sockets.length).to.eql(3);
+    });
 
-      it("returns all socket instances in the given room", async () => {
-        serverSockets[0].join(["room1", "room2"]);
-        serverSockets[1].join("room1");
-        serverSockets[2].join("room2");
-        const sockets = await io.in("room1").fetchSockets();
-        expect(sockets.length).to.eql(2);
-      });
+    it("returns all socket instances in the given room", async () => {
+      serverSockets[0].join(["room1", "room2"]);
+      serverSockets[1].join("room1");
+      serverSockets[2].join("room2");
+      const sockets = await io.in("room1").fetchSockets();
+      expect(sockets.length).to.eql(2);
+    });
 
-      it("works with a custom adapter", async () => {
-        io.adapter(DummyAdapter);
-        const sockets = await io.fetchSockets();
-        expect(sockets.length).to.eql(1);
-        const remoteSocket = sockets[0];
-        expect(remoteSocket.id).to.eql("42");
-        expect(remoteSocket.rooms).to.contain("42", "room1");
-        expect(remoteSocket.data).to.eql({ username: "john" });
+    it("works with a custom adapter", async () => {
+      io.adapter(DummyAdapter);
+      const sockets = await io.fetchSockets();
+      expect(sockets.length).to.eql(1);
+      const remoteSocket = sockets[0];
+      expect(remoteSocket.id).to.eql("42");
+      expect(remoteSocket.rooms).to.contain("42", "room1");
+      expect(remoteSocket.data).to.eql({ username: "john" });
+    });
+  });
+
+  describe("socketsJoin", () => {
+    it("makes all socket instances join the given room", () => {
+      io.socketsJoin("room1");
+      serverSockets.forEach((socket) => {
+        expect(socket.rooms).to.contain("room1");
       });
     });
 
-    describe("socketsJoin", () => {
-      it("makes all socket instances join the given room", () => {
-        io.socketsJoin("room1");
-        serverSockets.forEach((socket) => {
-          expect(socket.rooms).to.contain("room1");
-        });
-      });
+    it("makes all socket instances in a room join the given room", () => {
+      serverSockets[0].join(["room1", "room2"]);
+      serverSockets[1].join("room1");
+      serverSockets[2].join("room2");
+      io.in("room1").socketsJoin("room3");
+      expect(serverSockets[0].rooms).to.contain("room3");
+      expect(serverSockets[1].rooms).to.contain("room3");
+      expect(serverSockets[2].rooms).to.not.contain("room3");
+    });
+  });
 
-      it("makes all socket instances in a room join the given room", () => {
-        serverSockets[0].join(["room1", "room2"]);
-        serverSockets[1].join("room1");
-        serverSockets[2].join("room2");
-        io.in("room1").socketsJoin("room3");
-        expect(serverSockets[0].rooms).to.contain("room3");
-        expect(serverSockets[1].rooms).to.contain("room3");
-        expect(serverSockets[2].rooms).to.not.contain("room3");
-      });
+  describe("socketsLeave", () => {
+    it("makes all socket instances leave the given room", () => {
+      serverSockets[0].join(["room1", "room2"]);
+      serverSockets[1].join("room1");
+      serverSockets[2].join("room2");
+      io.socketsLeave("room1");
+      expect(serverSockets[0].rooms).to.contain("room2");
+      expect(serverSockets[0].rooms).to.not.contain("room1");
+      expect(serverSockets[1].rooms).to.not.contain("room1");
     });
 
-    describe("socketsLeave", () => {
-      it("makes all socket instances leave the given room", () => {
-        serverSockets[0].join(["room1", "room2"]);
-        serverSockets[1].join("room1");
-        serverSockets[2].join("room2");
-        io.socketsLeave("room1");
-        expect(serverSockets[0].rooms).to.contain("room2");
-        expect(serverSockets[0].rooms).to.not.contain("room1");
-        expect(serverSockets[1].rooms).to.not.contain("room1");
-      });
+    it("makes all socket instances in a room leave the given room", () => {
+      serverSockets[0].join(["room1", "room2"]);
+      serverSockets[1].join("room1");
+      serverSockets[2].join("room2");
+      io.in("room2").socketsLeave("room1");
+      expect(serverSockets[0].rooms).to.contain("room2");
+      expect(serverSockets[0].rooms).to.not.contain("room1");
+      expect(serverSockets[1].rooms).to.contain("room1");
+    });
+  });
 
-      it("makes all socket instances in a room leave the given room", () => {
-        serverSockets[0].join(["room1", "room2"]);
-        serverSockets[1].join("room1");
-        serverSockets[2].join("room2");
-        io.in("room2").socketsLeave("room1");
-        expect(serverSockets[0].rooms).to.contain("room2");
-        expect(serverSockets[0].rooms).to.not.contain("room1");
-        expect(serverSockets[1].rooms).to.contain("room1");
-      });
+  describe("disconnectSockets", () => {
+    it("makes all socket instances disconnect", (done) => {
+      io.disconnectSockets(true);
+
+      const partialDone = createPartialDone(3, done);
+
+      clientSockets[0].on("disconnect", partialDone);
+      clientSockets[1].on("disconnect", partialDone);
+      clientSockets[2].on("disconnect", partialDone);
     });
 
-    describe("disconnectSockets", () => {
-      it("makes all socket instances disconnect", (done) => {
-        io.disconnectSockets(true);
+    it("makes all socket instances in a room disconnect", (done) => {
+      serverSockets[0].join(["room1", "room2"]);
+      serverSockets[1].join("room1");
+      serverSockets[2].join("room2");
+      io.in("room2").disconnectSockets(true);
 
-        const partialDone = createPartialDone(3, done);
-
-        clientSockets[0].on("disconnect", partialDone);
-        clientSockets[1].on("disconnect", partialDone);
-        clientSockets[2].on("disconnect", partialDone);
+      const partialDone = createPartialDone(2, () => {
+        clientSockets[1].off("disconnect");
+        done();
       });
 
-      it("makes all socket instances in a room disconnect", (done) => {
-        serverSockets[0].join(["room1", "room2"]);
-        serverSockets[1].join("room1");
-        serverSockets[2].join("room2");
-        io.in("room2").disconnectSockets(true);
-
-        const partialDone = createPartialDone(2, done, () => {
-          clientSockets[1].off("disconnect");
-        });
-
-        clientSockets[0].on("disconnect", partialDone);
-        clientSockets[1].on("disconnect", () => {
-          done(new Error("should not happen"));
-        });
-        clientSockets[2].on("disconnect", partialDone);
+      clientSockets[0].on("disconnect", partialDone);
+      clientSockets[1].on("disconnect", () => {
+        done(new Error("should not happen"));
       });
+      clientSockets[2].on("disconnect", partialDone);
     });
   });
 });

test/uws.ts

@@ -1,4 +1,8 @@
-import { App, us_socket_local_port } from "uWebSockets.js";
+import {
+  App,
+  us_socket_local_port,
+  us_listen_socket_close,
+} from "uWebSockets.js";
 import { Server } from "..";
 import { io as ioc, Socket as ClientSocket } from "socket.io-client";
 import request from "supertest";
@@ -19,6 +23,7 @@ const shouldNotHappen = (done) => () => done(new Error("should not happen"));
 
 describe("socket.io with uWebSocket.js-based engine", () => {
   let io: Server,
+    uwsSocket: any,
     port: number,
     client: ClientSocket,
     clientWSOnly: ClientSocket,
@@ -33,6 +38,7 @@ describe("socket.io with uWebSocket.js-based engine", () => {
     io.of("/custom");
 
     app.listen(0, (listenSocket) => {
+      uwsSocket = listenSocket;
       port = us_socket_local_port(listenSocket);
 
       client = ioc(`http://localhost:${port}`);
@@ -47,13 +53,15 @@ describe("socket.io with uWebSocket.js-based engine", () => {
 
     const partialDone = createPartialDone(done, 4);
     client.on("connect", partialDone);
-    clientWSOnly.on("connect", partialDone);
+    clientWSOnly.once("connect", partialDone);
     clientPollingOnly.on("connect", partialDone);
     clientCustomNamespace.on("connect", partialDone);
   });
 
   afterEach(() => {
     io.close();
+    us_listen_socket_close(uwsSocket);
+
     client.disconnect();
     clientWSOnly.disconnect();
     clientPollingOnly.disconnect();
@@ -178,6 +186,12 @@ describe("socket.io with uWebSocket.js-based engine", () => {
     io.to("room1").emit("hello");
   });
 
+  it("should not crash when socket is disconnected before the upgrade", (done) => {
+    client.on("disconnect", () => done());
+
+    io.of("/").sockets.get(client.id)!.disconnect();
+  });
+
   it("should serve static files", (done) => {
     const clientVersion = require("socket.io-client/package.json").version;
 
@@ -186,7 +200,9 @@ describe("socket.io with uWebSocket.js-based engine", () => {
       .buffer(true)
       .end((err, res) => {
         if (err) return done(err);
-        expect(res.headers["content-type"]).to.be("application/javascript");
+        expect(res.headers["content-type"]).to.be(
+          "application/javascript; charset=utf-8"
+        );
         expect(res.headers.etag).to.be('"' + clientVersion + '"');
         expect(res.headers["x-sourcemap"]).to.be(undefined);
         expect(res.text).to.match(/engine\.io/);

test/v2-compatibility.ts

@@ -0,0 +1,64 @@
+import { Server, Socket } from "..";
+import expect from "expect.js";
+import { success, getPort, waitFor } from "./support/util";
+import * as io_v2 from "socket.io-client-v2";
+
+describe("v2 compatibility", () => {
+  it("should connect if `allowEIO3` is true", (done) => {
+    const io = new Server(0, {
+      allowEIO3: true,
+    });
+
+    const clientSocket = io_v2.connect(`http://localhost:${getPort(io)}`, {
+      multiplex: false,
+    });
+
+    Promise.all([
+      waitFor(io, "connection"),
+      waitFor(clientSocket, "connect"),
+    ]).then(([socket]) => {
+      expect((socket as Socket).id).to.eql(clientSocket.id);
+
+      success(done, io, clientSocket);
+    });
+  });
+
+  it("should be able to connect to a namespace with a query", (done) => {
+    const io = new Server(0, {
+      allowEIO3: true,
+    });
+
+    const clientSocket = io_v2.connect(
+      `http://localhost:${getPort(io)}/the-namespace`,
+      {
+        multiplex: false,
+      }
+    );
+    clientSocket.query = { test: "123" };
+
+    Promise.all([
+      waitFor(io.of("/the-namespace"), "connection"),
+      waitFor(clientSocket, "connect"),
+    ]).then(([socket]) => {
+      expect((socket as Socket).handshake.auth).to.eql({ test: "123" });
+
+      success(done, io, clientSocket);
+    });
+  });
+
+  it("should not connect if `allowEIO3` is false (default)", (done) => {
+    const io = new Server(0);
+
+    const clientSocket = io_v2.connect(`http://localhost:${getPort(io)}`, {
+      multiplex: false,
+    });
+
+    clientSocket.on("connect", () => {
+      done(new Error("should not happen"));
+    });
+
+    clientSocket.on("connect_error", () => {
+      success(done, io, clientSocket);
+    });
+  });
+});