chore(release): 4.7.0

Diff: https://github.com/socketio/socket.io/compare/4.6.2...4.7.0
ci: add Node.js 20 in the test matrix
2026-01-11 16:08:24 -05:00 · 2023-06-22 11:27:45 +02:00 · 2023-06-22 07:55:32 +02:00 · 2023-06-21 00:07:44 +02:00 · 2023-06-20 23:57:46 +02:00 · 2023-06-20 14:32:59 +02:00
43 changed files with 8340 additions and 8939 deletions
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,7 +16,9 @@ jobs:

    strategy:
      matrix:
-        node-version: [12, 14, 16]
+        node-version:
+          - 16
+          - 20

    steps:
      - name: Checkout repository
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # History

+## 2023
+
+- [4.7.0](#470-2023-06-22) (Jun 2023)
+- [4.6.2](#462-2023-05-31) (May 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)
@@ -52,6 +59,304 @@

 # Release notes

+## [4.7.0](https://github.com/socketio/socket.io/compare/4.6.2...4.7.0) (2023-06-22)
+
+
+### Bug Fixes
+
+* remove the Partial modifier from the socket.data type ([#4740](https://github.com/socketio/socket.io/issues/4740)) ([e5c62ca](https://github.com/socketio/socket.io/commit/e5c62cad60fc7d16fbb024fd9be1d1880f4e6f5f))
+
+
+### Features
+
+#### Support for WebTransport
+
+The Engine.IO server can now use WebTransport as the underlying transport.
+
+WebTransport is a web API that uses the HTTP/3 protocol as a bidirectional transport. It's intended for two-way communications between a web client and an HTTP/3 server.
+
+References:
+
+- https://w3c.github.io/webtransport/
+- https://developer.mozilla.org/en-US/docs/Web/API/WebTransport
+- https://developer.chrome.com/articles/webtransport/
+
+Until WebTransport support lands [in Node.js](https://github.com/nodejs/node/issues/38478), you can use the `@fails-components/webtransport` package:
+
+```js
+import { readFileSync } from "fs";
+import { createServer } from "https";
+import { Server } from "socket.io";
+import { Http3Server } from "@fails-components/webtransport";
+
+// WARNING: the total length of the validity period MUST NOT exceed two weeks (https://w3c.github.io/webtransport/#custom-certificate-requirements)
+const cert = readFileSync("/path/to/my/cert.pem");
+const key = readFileSync("/path/to/my/key.pem");
+
+const httpsServer = createServer({
+  key,
+  cert
+});
+
+httpsServer.listen(3000);
+
+const io = new Server(httpsServer, {
+  transports: ["polling", "websocket", "webtransport"] // WebTransport is not enabled by default
+});
+
+const h3Server = new Http3Server({
+  port: 3000,
+  host: "0.0.0.0",
+  secret: "changeit",
+  cert,
+  privKey: key,
+});
+
+(async () => {
+  const stream = await h3Server.sessionStream("/engine.io/");
+  const sessionReader = stream.getReader();
+
+  while (true) {
+    const { done, value } = await sessionReader.read();
+    if (done) {
+      break;
+    }
+    io.engine.onWebTransportSession(value);
+  }
+})();
+
+h3Server.startServer();
+```
+
+Added in [123b68c](https://github.com/socketio/engine.io/commit/123b68c04f9e971f59b526e0f967a488ee6b0116).
+
+
+#### Client bundles with CORS headers
+
+The bundles will now have the right `Access-Control-Allow-xxx` headers.
+
+Added in [63f181c](https://github.com/socketio/socket.io/commit/63f181cc12cbbbf94ed40eef52d60f36a1214fbe).
+
+
+### Dependencies
+
+- [`engine.io@~6.4.2`](https://github.com/socketio/engine.io/releases/tag/6.5.0) ([diff](https://github.com/socketio/engine.io/compare/6.4.2...6.5.0))
+- [`ws@~8.11.0`](https://github.com/websockets/ws/releases/tag/8.11.0) (no change)
+
+
+
+## [4.6.2](https://github.com/socketio/socket.io/compare/4.6.1...4.6.2) (2023-05-31)
+
+
+### Bug Fixes
+
+* **exports:** move `types` condition to the top ([#4698](https://github.com/socketio/socket.io/issues/4698)) ([3d44aae](https://github.com/socketio/socket.io/commit/3d44aae381af38349fdb808d510d9f47a0c2507e))
+
+
+### Dependencies
+
+- [`engine.io@~6.4.2`](https://github.com/socketio/engine.io/releases/tag/6.4.0) ([diff](https://github.com/socketio/engine.io/compare/6.4.1...6.4.2))
+- [`ws@~8.11.0`](https://github.com/websockets/ws/releases/tag/8.11.0) (no change)
+
+
+
+## [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@~6.4.1`](https://github.com/socketio/engine.io/releases/tag/6.4.1) ([diff](https://github.com/socketio/engine.io/compare/6.4.0...6.4.1))
+- [`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) (https://github.com/socketio/engine.io/compare/6.2.1...6.4.0)
+- [`ws@~8.11.0`](https://github.com/websockets/ws/releases/tag/8.11.0) (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:
@@ -61,8 +366,8 @@ This release contains a bump of:

 ### Dependencies

- [`engine.io@~6.2.1`](https://github.com/socketio/engine.io-client/tree/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)
+- [`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)



@@ -74,6 +379,11 @@ This release contains a bump of:
 * **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))

+### Dependencies
+
+- [`engine.io@~6.2.0`](https://github.com/socketio/engine.io/releases/tag/6.2.1) (no change)
+- [`ws@~8.2.3`](https://github.com/websockets/ws/releases/tag/8.2.3) (no change)
+


 ## [4.5.2](https://github.com/socketio/socket.io/compare/4.5.1...4.5.2) (2022-09-02)
@@ -84,13 +394,18 @@ This release contains a bump of:
 * 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))

+### Dependencies
+
+- [`engine.io@~6.2.0`](https://github.com/socketio/engine.io/releases/tag/6.2.0) (no change)
+- [`ws@~8.2.3`](https://github.com/websockets/ws/releases/tag/8.2.3) (no change)
+


 # [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.
+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)

@@ -102,6 +417,11 @@ Security advisory: [GHSA-j4f2-536g-r55m](https://github.com/advisories/GHSA-j4f2
 * 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))

+### Dependencies
+
+- [`engine.io@~3.6.0`](https://github.com/socketio/engine.io/releases/tag/3.6.0) (https://github.com/socketio/engine.io/compare/3.5.0...3.6.0)
+- [`ws@~7.4.2`](https://github.com/websockets/ws/releases/tag/7.4.2) (no change)
+


 ## [4.5.1](https://github.com/socketio/socket.io/compare/4.5.0...4.5.1) (2022-05-17)
@@ -112,6 +432,11 @@ Security advisory: [GHSA-j4f2-536g-r55m](https://github.com/advisories/GHSA-j4f2
 * forward the local flag to the adapter when using fetchSockets() ([30430f0](https://github.com/socketio/socket.io/commit/30430f0985f8e7c49394543d4c84913b6a15df60))
 * **typings:** add HTTPS server to accepted types ([#4351](https://github.com/socketio/socket.io/issues/4351)) ([9b43c91](https://github.com/socketio/socket.io/commit/9b43c9167cff817c60fa29dbda2ef7cd938aff51))

+### Dependencies
+
+- [`engine.io@~6.2.0`](https://github.com/socketio/engine.io/releases/tag/6.2.0) (no change)
+- [`ws@~8.2.3`](https://github.com/websockets/ws/releases/tag/8.2.3) (no change)
+


 # [4.5.0](https://github.com/socketio/socket.io/compare/4.4.1...4.5.0) (2022-04-23)
@@ -124,7 +449,7 @@ Security advisory: [GHSA-j4f2-536g-r55m](https://github.com/advisories/GHSA-j4f2

 ### Features

-* add support for catch-all listeners for outgoing packets ([531104d](https://github.com/socketio/socket.io/commit/531104d332690138b7aab84d5583d6204132c8b4))
+#### Catch-all listeners for outgoing packets

 This is similar to `onAny()`, but for outgoing packets.

@@ -136,7 +461,9 @@ socket.onAnyOutgoing((event, ...args) => {
 });
 ```

-* broadcast and expect multiple acks ([8b20457](https://github.com/socketio/socket.io/commit/8b204570a94979bbec307f23ca078f30f5cf07b0))
+Added in [531104d](https://github.com/socketio/socket.io/commit/531104d332690138b7aab84d5583d6204132c8b4).
+
+#### Broadcast and expect multiple acknowledgements

 Syntax:

@@ -146,18 +473,25 @@ io.timeout(1000).emit("some-event", (err, responses) => {
 });
 ```

-* add the "maxPayload" field in the handshake details ([088dcb4](https://github.com/socketio/engine.io/commit/088dcb4dff60df39785df13d0a33d3ceaa1dff38))
+Added in [8b20457](https://github.com/socketio/socket.io/commit/8b204570a94979bbec307f23ca078f30f5cf07b0).

-So that clients in HTTP long-polling can decide how many packets they have to send to stay under the maxHttpBufferSize
-value.
+#### `maxHttpBufferSize` value negotiation

-This is a backward compatible change which should not mandate a new major revision of the protocol (we stay in v4), as
-we only add a field in the JSON-encoded handshake data:
+A "maxPayload" field is now included in the Engine.IO handshake, so that clients in HTTP long-polling can decide how many packets they have to send to stay under the `maxHttpBufferSize` value.
+
+This is a backward compatible change which should not mandate a new major revision of the protocol (we stay in v4), as we only add a field in the JSON-encoded handshake data:

 ```
 0{"sid":"lv_VI97HAXpY6yYWAAAC","upgrades":["websocket"],"pingInterval":25000,"pingTimeout":5000,"maxPayload":1000000}
 ```

+Added in [088dcb4](https://github.com/socketio/engine.io/commit/088dcb4dff60df39785df13d0a33d3ceaa1dff38).
+
+### Dependencies
+
+- [`engine.io@~6.2.0`](https://github.com/socketio/engine.io/releases/tag/6.2.0) (https://github.com/socketio/engine.io/compare/6.1.0...6.2.0)
+- [`ws@~8.2.3`](https://github.com/websockets/ws/releases/tag/8.2.3) (no change)
+


 ## [4.4.1](https://github.com/socketio/socket.io/compare/4.4.0...4.4.1) (2022-01-06)
--- a/Readme.md
+++ b/Readme.md
@@ -126,7 +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
--- a/client-dist/socket.io.esm.min.js
+++ b/client-dist/socket.io.esm.min.js
--- a/client-dist/socket.io.esm.min.js.map
+++ b/client-dist/socket.io.esm.min.js.map
--- a/client-dist/socket.io.js
+++ b/client-dist/socket.io.js
--- a/client-dist/socket.io.js.map
+++ b/client-dist/socket.io.js.map
--- a/client-dist/socket.io.min.js
+++ b/client-dist/socket.io.min.js
--- a/client-dist/socket.io.min.js.map
+++ b/client-dist/socket.io.min.js.map
--- a/client-dist/socket.io.msgpack.min.js
+++ b/client-dist/socket.io.msgpack.min.js
--- a/client-dist/socket.io.msgpack.min.js.map
+++ b/client-dist/socket.io.msgpack.min.js.map
--- a/examples/basic-websocket-client/README.md
+++ b/examples/basic-websocket-client/README.md
@@ -0,0 +1,18 @@
+# Basic Socket.IO client
+
+Please check the associated guide: https://socket.io/how-to/build-a-basic-client
+
+Content:
+
+```
+├── bundle
+│   └── socket.io.min.js
+├── src
+│   └── index.js
+├── test
+│   └── index.js
+├── check-bundle-size.js
+├── package.json
+├── README.md
+└── rollup.config.js
+```
--- a/examples/basic-websocket-client/bundle/socket.io.min.js
+++ b/examples/basic-websocket-client/bundle/socket.io.min.js
@@ -0,0 +1 @@
+class e{#e=new Map;on(e,t){let s=this.#e.get(e);s||this.#e.set(e,s=[]),s.push(t)}emit(e,...t){const s=this.#e.get(e);if(s)for(const e of s)e.apply(null,t)}}const t="0",s="1",n="2",i="3",o="4",r={CONNECT:0,DISCONNECT:1,EVENT:2};function c(){}class a extends e{id;connected=!1;#t;#s;#n;#i;#o;#r=[];#c;#a=!0;constructor(e,t){super(),this.#t=e,this.#s=Object.assign({path:"/socket.io/",reconnectionDelay:2e3},t),this.#h()}#h(){this.#n=new WebSocket(this.#u()),this.#n.onmessage=({data:e})=>this.#p(e),this.#n.onerror=c,this.#n.onclose=()=>this.#l("transport close")}#u(){return`${this.#t.replace(/^http/,"ws")}${this.#s.path}?EIO=4&transport=websocket`}#p(e){if("string"==typeof e)switch(e[0]){case t:this.#d(e);break;case s:this.#l("transport close");break;case n:this.#T(),this.#m(i);break;case o:let c;try{c=function(e){let t=1;const s={type:parseInt(e.charAt(t++),10)};e.charAt(t)&&(s.data=JSON.parse(e.substring(t)));if(!function(e){switch(e.type){case r.CONNECT:return"object"==typeof e.data;case r.DISCONNECT:return void 0===e.data;case r.EVENT:{const t=e.data;return Array.isArray(t)&&t.length>0&&"string"==typeof t[0]}default:return!1}}(s))throw new Error("invalid format");return s}(e)}catch(e){return this.#l("parse error")}this.#f(c);break;default:this.#l("parse error")}}#d(e){let t;try{t=JSON.parse(e.substring(1))}catch(e){return this.#l("parse error")}this.#o=t.pingInterval+t.pingTimeout,this.#T(),this.#C()}#f(e){switch(e.type){case r.CONNECT:this.#g(e);break;case r.DISCONNECT:this.#a=!1,this.#l("io server disconnect");break;case r.EVENT:super.emit.apply(this,e.data);break;default:this.#l("parse error")}}#g(e){this.id=e.data.sid,this.connected=!0,this.#r.forEach((e=>this.#y(e))),this.#r.slice(0),super.emit("connect")}#l(e){this.#n&&(this.#n.onclose=c,this.#n.close()),clearTimeout(this.#i),clearTimeout(this.#c),this.connected?(this.connected=!1,this.id=void 0,super.emit("disconnect",e)):super.emit("connect_error",e),this.#a&&(this.#c=setTimeout((()=>this.#h()),this.#s.reconnectionDelay))}#T(){clearTimeout(this.#i),this.#i=setTimeout((()=>{this.#l("ping timeout")}),this.#o)}#m(e){this.#n.readyState===WebSocket.OPEN&&this.#n.send(e)}#y(e){this.#m(o+function(e){let t=""+e.type;e.data&&(t+=JSON.stringify(e.data));return t}(e))}#C(){this.#y({type:r.CONNECT})}emit(...e){const t={type:r.EVENT,data:e};this.connected?this.#y(t):this.#r.push(t)}disconnect(){this.#a=!1,this.#l("io client disconnect")}}function h(e,t){return"string"!=typeof e&&(t=e,e=location.origin),new a(e,t)}export{h as io};
--- a/examples/basic-websocket-client/check-bundle-size.js
+++ b/examples/basic-websocket-client/check-bundle-size.js
@@ -0,0 +1,17 @@
+import { rollup } from "rollup";
+import terser from "@rollup/plugin-terser";
+import { brotliCompressSync } from "node:zlib";
+
+const rollupBuild = await rollup({
+  input: "./src/index.js"
+});
+
+const rollupOutput = await rollupBuild.generate({
+  format: "esm",
+  plugins: [terser()],
+});
+
+const bundleAsString = rollupOutput.output[0].code;
+const brotliedBundle = brotliCompressSync(Buffer.from(bundleAsString));
+
+console.log(`Bundle size: ${brotliedBundle.length} B`);
--- a/examples/basic-websocket-client/package.json
+++ b/examples/basic-websocket-client/package.json
@@ -0,0 +1,18 @@
+{
+  "type": "module",
+  "devDependencies": {
+    "@rollup/plugin-terser": "^0.4.0",
+    "chai": "^4.3.7",
+    "mocha": "^10.2.0",
+    "prettier": "^2.8.4",
+    "rollup": "^3.20.2",
+    "socket.io": "^4.6.1",
+    "ws": "^8.13.0"
+  },
+  "scripts": {
+    "bundle": "rollup -c",
+    "check-bundle-size": "node check-bundle-size.js",
+    "format": "prettier -w src/ test/",
+    "test": "mocha"
+  }
+}
--- a/examples/basic-websocket-client/rollup.config.js
+++ b/examples/basic-websocket-client/rollup.config.js
@@ -0,0 +1,10 @@
+import terser from "@rollup/plugin-terser";
+
+export default {
+  input: "./src/index.js",
+  output: {
+    file: "./bundle/socket.io.min.js",
+    format: "esm",
+    plugins: [terser()],
+  }
+};
--- a/examples/basic-websocket-client/src/index.js
+++ b/examples/basic-websocket-client/src/index.js
@@ -0,0 +1,273 @@
+class EventEmitter {
+  #listeners = new Map();
+
+  on(event, listener) {
+    let listeners = this.#listeners.get(event);
+    if (!listeners) {
+      this.#listeners.set(event, (listeners = []));
+    }
+    listeners.push(listener);
+  }
+
+  emit(event, ...args) {
+    const listeners = this.#listeners.get(event);
+    if (listeners) {
+      for (const listener of listeners) {
+        listener.apply(null, args);
+      }
+    }
+  }
+}
+
+const EIOPacketType = {
+  OPEN: "0",
+  CLOSE: "1",
+  PING: "2",
+  PONG: "3",
+  MESSAGE: "4",
+};
+
+const SIOPacketType = {
+  CONNECT: 0,
+  DISCONNECT: 1,
+  EVENT: 2,
+};
+
+function noop() {}
+
+class Socket extends EventEmitter {
+  id;
+  connected = false;
+
+  #uri;
+  #opts;
+  #ws;
+  #pingTimeoutTimer;
+  #pingTimeoutDelay;
+  #sendBuffer = [];
+  #reconnectTimer;
+  #shouldReconnect = true;
+
+  constructor(uri, opts) {
+    super();
+    this.#uri = uri;
+    this.#opts = Object.assign(
+      {
+        path: "/socket.io/",
+        reconnectionDelay: 2000,
+      },
+      opts
+    );
+    this.#open();
+  }
+
+  #open() {
+    this.#ws = new WebSocket(this.#createUrl());
+    this.#ws.onmessage = ({ data }) => this.#onMessage(data);
+    // dummy handler for Node.js
+    this.#ws.onerror = noop;
+    this.#ws.onclose = () => this.#onClose("transport close");
+  }
+
+  #createUrl() {
+    const uri = this.#uri.replace(/^http/, "ws");
+    const queryParams = "?EIO=4&transport=websocket";
+    return `${uri}${this.#opts.path}${queryParams}`;
+  }
+
+  #onMessage(data) {
+    if (typeof data !== "string") {
+      // TODO handle binary payloads
+      return;
+    }
+
+    switch (data[0]) {
+      case EIOPacketType.OPEN:
+        this.#onOpen(data);
+        break;
+
+      case EIOPacketType.CLOSE:
+        this.#onClose("transport close");
+        break;
+
+      case EIOPacketType.PING:
+        this.#resetPingTimeout();
+        this.#send(EIOPacketType.PONG);
+        break;
+
+      case EIOPacketType.MESSAGE:
+        let packet;
+        try {
+          packet = decode(data);
+        } catch (e) {
+          return this.#onClose("parse error");
+        }
+        this.#onPacket(packet);
+        break;
+
+      default:
+        this.#onClose("parse error");
+        break;
+    }
+  }
+
+  #onOpen(data) {
+    let handshake;
+    try {
+      handshake = JSON.parse(data.substring(1));
+    } catch (e) {
+      return this.#onClose("parse error");
+    }
+    this.#pingTimeoutDelay = handshake.pingInterval + handshake.pingTimeout;
+    this.#resetPingTimeout();
+    this.#doConnect();
+  }
+
+  #onPacket(packet) {
+    switch (packet.type) {
+      case SIOPacketType.CONNECT:
+        this.#onConnect(packet);
+        break;
+
+      case SIOPacketType.DISCONNECT:
+        this.#shouldReconnect = false;
+        this.#onClose("io server disconnect");
+        break;
+
+      case SIOPacketType.EVENT:
+        super.emit.apply(this, packet.data);
+        break;
+
+      default:
+        this.#onClose("parse error");
+        break;
+    }
+  }
+
+  #onConnect(packet) {
+    this.id = packet.data.sid;
+    this.connected = true;
+
+    this.#sendBuffer.forEach((packet) => this.#sendPacket(packet));
+    this.#sendBuffer.slice(0);
+
+    super.emit("connect");
+  }
+
+  #onClose(reason) {
+    if (this.#ws) {
+      this.#ws.onclose = noop;
+      this.#ws.close();
+    }
+
+    clearTimeout(this.#pingTimeoutTimer);
+    clearTimeout(this.#reconnectTimer);
+
+    if (this.connected) {
+      this.connected = false;
+      this.id = undefined;
+      super.emit("disconnect", reason);
+    } else {
+      super.emit("connect_error", reason);
+    }
+
+    if (this.#shouldReconnect) {
+      this.#reconnectTimer = setTimeout(
+        () => this.#open(),
+        this.#opts.reconnectionDelay
+      );
+    }
+  }
+
+  #resetPingTimeout() {
+    clearTimeout(this.#pingTimeoutTimer);
+    this.#pingTimeoutTimer = setTimeout(() => {
+      this.#onClose("ping timeout");
+    }, this.#pingTimeoutDelay);
+  }
+
+  #send(data) {
+    if (this.#ws.readyState === WebSocket.OPEN) {
+      this.#ws.send(data);
+    }
+  }
+
+  #sendPacket(packet) {
+    this.#send(EIOPacketType.MESSAGE + encode(packet));
+  }
+
+  #doConnect() {
+    this.#sendPacket({ type: SIOPacketType.CONNECT });
+  }
+
+  emit(...args) {
+    const packet = {
+      type: SIOPacketType.EVENT,
+      data: args,
+    };
+
+    if (this.connected) {
+      this.#sendPacket(packet);
+    } else {
+      this.#sendBuffer.push(packet);
+    }
+  }
+
+  disconnect() {
+    this.#shouldReconnect = false;
+    this.#onClose("io client disconnect");
+  }
+}
+
+function encode(packet) {
+  let output = "" + packet.type;
+
+  if (packet.data) {
+    output += JSON.stringify(packet.data);
+  }
+
+  return output;
+}
+
+function decode(data) {
+  let i = 1; // skip "4" prefix
+
+  const packet = {
+    type: parseInt(data.charAt(i++), 10),
+  };
+
+  if (data.charAt(i)) {
+    packet.data = JSON.parse(data.substring(i));
+  }
+
+  if (!isPacketValid(packet)) {
+    throw new Error("invalid format");
+  }
+
+  return packet;
+}
+
+function isPacketValid(packet) {
+  switch (packet.type) {
+    case SIOPacketType.CONNECT:
+      return typeof packet.data === "object";
+    case SIOPacketType.DISCONNECT:
+      return packet.data === undefined;
+    case SIOPacketType.EVENT: {
+      const args = packet.data;
+      return (
+        Array.isArray(args) && args.length > 0 && typeof args[0] === "string"
+      );
+    }
+    default:
+      return false;
+  }
+}
+
+export function io(uri, opts) {
+  if (typeof uri !== "string") {
+    opts = uri;
+    uri = location.origin;
+  }
+  return new Socket(uri, opts);
+}
--- a/examples/basic-websocket-client/test/index.js
+++ b/examples/basic-websocket-client/test/index.js
@@ -0,0 +1,162 @@
+import { createServer } from "node:http";
+import { io as ioc } from "../src/index.js";
+import { WebSocket } from "ws";
+import { Server } from "socket.io";
+import { expect } from "chai";
+
+// @ts-ignore for Node.js
+globalThis.WebSocket = WebSocket;
+
+function waitFor(emitter, eventName) {
+  return new Promise((resolve) => {
+    emitter.on(eventName, resolve);
+  });
+}
+
+function sleep(delay) {
+  return new Promise((resolve) => {
+    setTimeout(resolve, delay);
+  });
+}
+
+describe("basic client", () => {
+  let io, port, socket;
+
+  beforeEach(() => {
+    const httpServer = createServer();
+    io = new Server(httpServer);
+
+    httpServer.listen(0);
+    port = httpServer.address().port;
+  });
+
+  afterEach(() => {
+    io.close();
+    socket.disconnect();
+  });
+
+  it("should connect", async () => {
+    socket = ioc(`ws://localhost:${port}`);
+
+    await waitFor(socket, "connect");
+
+    expect(socket.connected).to.eql(true);
+    expect(socket.id).to.be.a("string");
+  });
+
+  it("should connect with 'http://' scheme", async () => {
+    socket = ioc(`http://localhost:${port}`);
+
+    await waitFor(socket, "connect");
+  });
+
+  it("should connect with URL inferred from 'window.location'", async () => {
+    globalThis.location = {
+      origin: `http://localhost:${port}`,
+    };
+    socket = ioc();
+
+    await waitFor(socket, "connect");
+  });
+
+  it("should fail to connect to an invalid URL", async () => {
+    socket = ioc(`http://localhost:4321`);
+
+    await waitFor(socket, "connect_error");
+  });
+
+  it("should receive an event", async () => {
+    io.on("connection", (socket) => {
+      socket.emit("foo", 123);
+    });
+
+    socket = ioc(`ws://localhost:${port}`);
+
+    const value = await waitFor(socket, "foo");
+
+    expect(value).to.eql(123);
+  });
+
+  it("should send an event (not buffered)", async () => {
+    socket = ioc(`ws://localhost:${port}`);
+
+    const [serverSocket] = await Promise.all([
+      waitFor(io, "connection"),
+      waitFor(socket, "connect"),
+    ]);
+
+    socket.emit("foo", 456);
+
+    const value = await waitFor(serverSocket, "foo");
+
+    expect(value).to.eql(456);
+  });
+
+  it("should send an event (buffered)", async () => {
+    socket = ioc(`ws://localhost:${port}`);
+
+    socket.emit("foo", 789);
+
+    const [serverSocket] = await Promise.all([
+      waitFor(io, "connection"),
+      waitFor(socket, "connect"),
+    ]);
+
+    const value = await waitFor(serverSocket, "foo");
+
+    expect(value).to.eql(789);
+  });
+
+  it("should reconnect", async () => {
+    socket = ioc(`ws://localhost:${port}`, {
+      reconnectionDelay: 50,
+    });
+
+    await waitFor(socket, "connect");
+
+    io.close();
+
+    await waitFor(socket, "disconnect");
+
+    io.listen(port);
+
+    await waitFor(socket, "connect");
+  });
+
+  it("should respond to PING packets", async () => {
+    io.engine.opts.pingInterval = 50;
+    io.engine.opts.pingTimeout = 20;
+
+    socket = ioc(`ws://localhost:${port}`);
+
+    await waitFor(socket, "connect");
+
+    await sleep(500);
+
+    expect(socket.connected).to.eql(true);
+  });
+
+  it("should disconnect (client side)", async () => {
+    socket = ioc(`ws://localhost:${port}`);
+
+    await waitFor(socket, "connect");
+
+    socket.disconnect();
+
+    expect(socket.connected).to.eql(false);
+    expect(socket.id).to.eql(undefined);
+  });
+
+  it("should disconnect (server side)", async () => {
+    socket = ioc(`ws://localhost:${port}`);
+
+    const [serverSocket] = await Promise.all([
+      waitFor(io, "connection"),
+      waitFor(socket, "connect"),
+    ]);
+
+    serverSocket.disconnect();
+
+    await waitFor(socket, "disconnect");
+  });
+});
--- a/examples/cluster-haproxy/docker-compose.yml
+++ b/examples/cluster-haproxy/docker-compose.yml
@@ -1,51 +1,53 @@
+services:
+  haproxy:
+    image: haproxy:1.7-alpine
+    volumes:
+      - ./haproxy.cfg:/usr/local/etc/haproxy/haproxy.cfg:ro
+    links:
+      - server-john
+      - server-paul
+      - server-george
+      - server-ringo
+    ports:
+     - "3000:80"

-haproxy:
-  build: ./haproxy
-  links:
-    - server-john
-    - server-paul
-    - server-george
-    - server-ringo
-  ports:
-   - "3000:80"
+  server-john:
+    build: ./server
+    links:
+      - redis
+    expose:
+      - "3000"
+    environment:
+      - NAME=John

-server-john:
-  build: ./server
-  links:
-    - redis
-  expose:
-    - "3000"
-  environment:
-    - NAME=John
+  server-paul:
+    build: ./server
+    links:
+      - redis
+    expose:
+      - "3000"
+    environment:
+      - NAME=Paul

-server-paul:
-  build: ./server
-  links:
-    - redis
-  expose:
-    - "3000"
-  environment:
-    - NAME=Paul
+  server-george:
+    build: ./server
+    links:
+      - redis
+    expose:
+      - "3000"
+    environment:
+      - NAME=George

-server-george:
-  build: ./server
-  links:
-    - redis
-  expose:
-    - "3000"
-  environment:
-    - NAME=George
+  server-ringo:
+    build: ./server
+    links:
+      - redis
+    expose:
+      - "3000"
+    environment:
+      - NAME=Ringo

-server-ringo:
-  build: ./server
-  links:
-    - redis
-  expose:
-    - "3000"
-  environment:
-    - NAME=Ringo
-
-redis:
-  image: redis:alpine
-  expose:
-    - "6379"
+  redis:
+    image: redis:alpine
+    expose:
+      - "6379"
--- a/examples/cluster-haproxy/haproxy/haproxy.cfg
+++ b/examples/cluster-haproxy/haproxy/haproxy.cfg
--- a/examples/cluster-haproxy/haproxy/Dockerfile
+++ b/examples/cluster-haproxy/haproxy/Dockerfile
@@ -1,2 +0,0 @@
-FROM haproxy:1.7-alpine
-COPY haproxy.cfg /usr/local/etc/haproxy/haproxy.cfg
--- a/examples/cluster-httpd/docker-compose.yml
+++ b/examples/cluster-httpd/docker-compose.yml
@@ -1,51 +1,53 @@
+services:
+  httpd:
+    image: httpd:2.4-alpine
+    volumes:
+      - ./httpd.conf:/usr/local/apache2/conf/httpd.conf:ro
+    links:
+      - server-john
+      - server-paul
+      - server-george
+      - server-ringo
+    ports:
+     - "3000:80"

-httpd:
-  build: ./httpd
-  links:
-    - server-john
-    - server-paul
-    - server-george
-    - server-ringo
-  ports:
-   - "3000:80"
+  server-john:
+    build: ./server
+    links:
+      - redis
+    expose:
+      - "3000"
+    environment:
+      - NAME=John

-server-john:
-  build: ./server
-  links:
-    - redis
-  expose:
-    - "3000"
-  environment:
-    - NAME=John
+  server-paul:
+    build: ./server
+    links:
+      - redis
+    expose:
+      - "3000"
+    environment:
+      - NAME=Paul

-server-paul:
-  build: ./server
-  links:
-    - redis
-  expose:
-    - "3000"
-  environment:
-    - NAME=Paul
+  server-george:
+    build: ./server
+    links:
+      - redis
+    expose:
+      - "3000"
+    environment:
+      - NAME=George

-server-george:
-  build: ./server
-  links:
-    - redis
-  expose:
-    - "3000"
-  environment:
-    - NAME=George
+  server-ringo:
+    build: ./server
+    links:
+      - redis
+    expose:
+      - "3000"
+    environment:
+      - NAME=Ringo

-server-ringo:
-  build: ./server
-  links:
-    - redis
-  expose:
-    - "3000"
-  environment:
-    - NAME=Ringo
-
-redis:
-  image: redis:alpine
-  expose:
-    - "6379"
+  redis:
+    image: redis:6
+    expose:
+      - "6379"
--- a/examples/cluster-httpd/httpd/httpd.conf
+++ b/examples/cluster-httpd/httpd/httpd.conf
@@ -51,4 +51,5 @@ RewriteRule /(.*) balancer://nodes_ws/$1 [P,L]
 RewriteCond %{HTTP:Upgrade} !=websocket [NC]
 RewriteRule /(.*) balancer://nodes_polling/$1 [P,L]

-ProxyTimeout 3
+# must be bigger than pingInterval (25s by default) + pingTimeout (20s by default)
+ProxyTimeout 60
--- a/examples/cluster-httpd/httpd/Dockerfile
+++ b/examples/cluster-httpd/httpd/Dockerfile
@@ -1,2 +0,0 @@
-FROM httpd:2.4-alpine
-COPY ./httpd.conf /usr/local/apache2/conf/httpd.conf
--- a/examples/cluster-httpd/server/Dockerfile
+++ b/examples/cluster-httpd/server/Dockerfile
@@ -1,4 +1,4 @@
-FROM mhart/alpine-node:6
+FROM node:14-alpine

 # Create app directory
 RUN mkdir -p /usr/src/app
--- a/examples/cluster-nginx/docker-compose.yml
+++ b/examples/cluster-nginx/docker-compose.yml
@@ -1,58 +1,58 @@
+services:
+  nginx:
+    image: nginx:alpine
+    volumes:
+      - ./nginx.conf:/etc/nginx/nginx.conf:ro
+    links:
+      - server-john
+      - server-paul
+      - server-george
+      - server-ringo
+    ports:
+     - "3000:80"

-nginx:
-  image: nginx:alpine
-  volumes:
-    - ./nginx.conf:/etc/nginx/nginx.conf:ro
-  links:
-    - server-john
-    - server-paul
-    - server-george
-    - server-ringo
-  ports:
-   - "3000:80"
+  server-john:
+    build: ./server
+    links:
+      - redis
+    expose:
+      - "3000"
+    environment:
+      - NAME=John

-server-john:
-  build: ./server
-  links:
-    - redis
-  expose:
-    - "3000"
-  environment:
-    - NAME=John
+  server-paul:
+    build: ./server
+    links:
+      - redis
+    expose:
+      - "3000"
+    environment:
+      - NAME=Paul

-server-paul:
-  build: ./server
-  links:
-    - redis
-  expose:
-    - "3000"
-  environment:
-    - NAME=Paul
+  server-george:
+    build: ./server
+    links:
+      - redis
+    expose:
+      - "3000"
+    environment:
+      - NAME=George

-server-george:
-  build: ./server
-  links:
-    - redis
-  expose:
-    - "3000"
-  environment:
-    - NAME=George
+  server-ringo:
+    build: ./server
+    links:
+      - redis
+    expose:
+      - "3000"
+    environment:
+      - NAME=Ringo

-server-ringo:
-  build: ./server
-  links:
-    - redis
-  expose:
-    - "3000"
-  environment:
-    - NAME=Ringo
+  client:
+    build: ./client
+    links:
+      - nginx

-client:
-  build: ./client
-  links:
-    - nginx
-
-redis:
-  image: redis:alpine
-  expose:
-    - "6379"
+  redis:
+    image: redis:6
+    expose:
+      - "6379"
--- a/examples/create-react-app-example/package.json
+++ b/examples/create-react-app-example/package.json
@@ -3,14 +3,14 @@
  "version": "0.1.0",
  "private": true,
  "dependencies": {
-    "@testing-library/jest-dom": "^4.2.4",
-    "@testing-library/react": "^9.3.2",
-    "@testing-library/user-event": "^7.1.2",
-    "react": "^16.13.1",
-    "react-dom": "^16.13.1",
-    "react-scripts": "3.4.1",
-    "socket.io": "4",
-    "socket.io-client": "4"
+    "@testing-library/jest-dom": "^5.16.5",
+    "@testing-library/react": "^14.0.0",
+    "@testing-library/user-event": "^14.4.3",
+    "react": "^18.2.0",
+    "react-dom": "^18.2.0",
+    "react-scripts": "^5.0.1",
+    "socket.io": "^4.6.1",
+    "socket.io-client": "^4.6.1"
  },
  "scripts": {
    "start": "react-scripts start",
--- a/examples/create-react-app-example/src/index.js
+++ b/examples/create-react-app-example/src/index.js
@@ -1,14 +1,15 @@
 import React from 'react';
-import ReactDOM from 'react-dom';
+import { createRoot } from 'react-dom/client';
 import './index.css';
 import App from './App';
 import * as serviceWorker from './serviceWorker';

-ReactDOM.render(
+const container = document.getElementById('root');
+const root = createRoot(container)
+root.render(
  <React.StrictMode>
    <App />
-  </React.StrictMode>,
-  document.getElementById('root')
+  </React.StrictMode>
 );

 // If you want your app to work offline and load faster, you can change
--- a/examples/create-react-app-example/yarn.lock
+++ b/examples/create-react-app-example/yarn.lock
--- a/examples/private-messaging/package.json
+++ b/examples/private-messaging/package.json
@@ -8,18 +8,19 @@
    "lint": "vue-cli-service lint"
  },
  "dependencies": {
-    "core-js": "^3.6.5",
+    "core-js": "^3.8.3",
    "socket.io-client": "^4.0.0",
-    "vue": "^2.6.11"
+    "vue": "^2.6.14"
  },
  "devDependencies": {
-    "@vue/cli-plugin-babel": "~4.5.0",
-    "@vue/cli-plugin-eslint": "~4.5.0",
-    "@vue/cli-service": "~4.5.0",
-    "babel-eslint": "^10.1.0",
-    "eslint": "^6.7.2",
-    "eslint-plugin-vue": "^6.2.2",
-    "vue-template-compiler": "^2.6.11"
+    "@babel/core": "^7.12.16",
+    "@babel/eslint-parser": "^7.12.16",
+    "@vue/cli-plugin-babel": "~5.0.0",
+    "@vue/cli-plugin-eslint": "~5.0.0",
+    "@vue/cli-service": "~5.0.0",
+    "eslint": "^7.32.0",
+    "eslint-plugin-vue": "^8.0.3",
+    "vue-template-compiler": "^2.6.14"
  },
  "eslintConfig": {
    "root": true,
@@ -31,9 +32,11 @@
      "eslint:recommended"
    ],
    "parserOptions": {
-      "parser": "babel-eslint"
+      "parser": "@babel/eslint-parser"
    },
-    "rules": {}
+    "rules": {
+      "vue/multi-word-component-names": "off"
+    }
  },
  "browserslist": [
    "> 1%",
--- a/examples/private-messaging/src/App.vue
+++ b/examples/private-messaging/src/App.vue
@@ -68,7 +68,7 @@ body {

@font-face {
  font-family: Lato;
-  src: url("/fonts/Lato-Regular.ttf");
+  src: "~/public/fonts/Lato-Regular.ttf";
 }

 #app {
--- a/lib/client.ts
+++ b/lib/client.ts
@@ -311,9 +311,13 @@ export class Client<
   * Called upon transport close.
   *
   * @param reason
+   * @param description
   * @private
   */
-  private onclose(reason: CloseReason | "forced server close"): void {
+  private onclose(
+    reason: CloseReason | "forced server close",
+    description?: any
+  ): void {
    debug("client close with reason %s", reason);

    // ignore a potential subsequent `close` event
@@ -321,7 +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();

--- a/lib/index.ts
+++ b/lib/index.ts
@@ -6,12 +6,11 @@ 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";
@@ -41,7 +40,7 @@ import {
  SecondArg,
 } from "./typed-events";
 import { patchAdapter, restoreAdapter, serveFile } from "./uws";
-import type { BaseServer } from "engine.io/build/server";
+import corsMiddleware from "cors";

 const debug = debugModule("socket.io:server");

@@ -180,6 +179,18 @@ 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 readonly opts: Partial<ServerOptions>;
@@ -192,6 +203,11 @@ export class Server<
   */
  _connectTimeout: number;
  private httpServer: http.Server | HTTPSServer | Http2SecureServer;
+  private _corsMiddleware: (
+    req: http.IncomingMessage,
+    res: http.ServerResponse,
+    next: () => void
+  ) => void;

  /**
   * Server constructor.
@@ -257,6 +273,10 @@ export class Server<
      this.attach(
        srv as http.Server | HTTPSServer | Http2SecureServer | number
      );
+
+    if (this.opts.cors) {
+      this._corsMiddleware = corsMiddleware(this.opts.cors);
+    }
  }

  get _opts() {
@@ -316,8 +336,6 @@ 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);
      });
    };
@@ -540,7 +558,13 @@ export class Server<
    srv.removeAllListeners("request");
    srv.on("request", (req, res) => {
      if (this.clientPathRegex.test(req.url!)) {
-        this.serve(req, res);
+        if (this._corsMiddleware) {
+          this._corsMiddleware(req, res, () => {
+            this.serve(req, res);
+          });
+        } else {
+          this.serve(req, res);
+        }
      } else {
        for (let i = 0; i < evs.length; i++) {
          evs[i].call(srv, req, res);
@@ -693,6 +717,7 @@ export class Server<
          (nsp, conn, next) => next(null, (name as RegExp).test(nsp)),
          parentNsp
        );
+        this.parentNamespacesFromRegExp.set(name, parentNsp);
      }
      if (fn) {
        // @ts-ignore
@@ -705,6 +730,13 @@ 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);
--- a/lib/namespace.ts
+++ b/lib/namespace.ts
@@ -358,12 +358,15 @@ export class Namespace<
      typeof sessionId === "string" &&
      typeof offset === "string"
    ) {
-      const session = await this.adapter.restoreSession(sessionId, offset);
+      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);
-      } else {
-        debug("unable to restore session state");
      }
    }
    return new Socket(this, client, auth);
--- a/lib/parent-namespace.ts
+++ b/lib/parent-namespace.ts
@@ -11,6 +11,21 @@ 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,
@@ -81,6 +96,10 @@ export class ParentNamespace<
    }

    this.server._nsps.set(name, namespace);
+
+    // @ts-ignore
+    this.server.sockets.emitReserved("new_namespace", namespace);
+
    return namespace;
  }

--- a/lib/socket.ts
+++ b/lib/socket.ts
@@ -56,8 +56,8 @@ const RECOVERABLE_DISCONNECT_REASONS: ReadonlySet<DisconnectReason> = new Set([
 ]);

 export interface SocketReservedEventsMap {
-  disconnect: (reason: DisconnectReason) => void;
-  disconnecting: (reason: DisconnectReason) => void;
+  disconnect: (reason: DisconnectReason, description?: any) => void;
+  disconnecting: (reason: DisconnectReason, description?: any) => void;
  error: (err: Error) => void;
 }

@@ -202,7 +202,7 @@ export class Socket<
   * 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> = {};
+  public data: SocketData = {} as SocketData;
  /**
   * Whether the socket is currently connected or not.
   *
@@ -260,7 +260,7 @@ export class Socket<
      this.id = previousSession.sid;
      this.pid = previousSession.pid;
      previousSession.rooms.forEach((room) => this.join(room));
-      this.data = previousSession.data as Partial<SocketData>;
+      this.data = previousSession.data as SocketData;
      previousSession.missedPackets.forEach((packet) => {
        this.packet({
          type: PacketType.EVENT,
@@ -275,9 +275,14 @@ export class Socket<
      } else {
        this.id = base64id.generateId(); // don't reuse the Engine.IO id because it's sensitive information
      }
-      this.pid = base64id.generateId();
+      if (this.server._opts.connectionStateRecovery) {
+        this.pid = base64id.generateId();
+      }
    }
    this.handshake = this.buildHandshake(auth);
+
+    // prevents crash when the socket receives an "error" event without listener
+    this.on("error", noop);
  }

  /**
@@ -718,28 +723,31 @@ export class Socket<
   * @private
   */
  _onerror(err: Error): void {
-    if (this.listeners("error").length) {
-      this.emitReserved("error", err);
-    } else {
-      console.error("Missing error handler on `socket`.");
-      console.error(err.stack);
-    }
+    // FIXME the meaning of the "error" event is overloaded:
+    //  - it can be sent by the client (`socket.emit("error")`)
+    //  - it can be emitted when the connection encounters an error (an invalid packet for example)
+    //  - it can be emitted when a packet is rejected in a middleware (`socket.use()`)
+    this.emitReserved("error", err);
  }

  /**
   * Called upon closing. Called by `Client`.
   *
   * @param {String} reason
+   * @param description
   * @throw {Error} optional error object
   *
   * @private
   */
-  _onclose(reason: DisconnectReason): 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.emitReserved("disconnecting", reason, description);

-    if (RECOVERABLE_DISCONNECT_REASONS.has(reason)) {
+    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,
@@ -753,7 +761,7 @@ export class Socket<
    this.nsp._remove(this);
    this.client._remove(this);
    this.connected = false;
-    this.emitReserved("disconnect", reason);
+    this.emitReserved("disconnect", reason, description);
    return;
  }

--- a/package-lock.json
+++ b/package-lock.json
@@ -1,20 +1,21 @@
 {
  "name": "socket.io",
-  "version": "4.5.4",
+  "version": "4.6.2",
  "lockfileVersion": 2,
  "requires": true,
  "packages": {
    "": {
      "name": "socket.io",
-      "version": "4.5.4",
+      "version": "4.6.2",
      "license": "MIT",
      "dependencies": {
        "accepts": "~1.3.4",
        "base64id": "~2.0.0",
+        "cors": "~2.8.5",
        "debug": "~4.3.2",
-        "engine.io": "~6.3.1",
+        "engine.io": "~6.5.0",
        "socket.io-adapter": "~2.5.2",
-        "socket.io-parser": "~4.2.1"
+        "socket.io-parser": "~4.2.4"
      },
      "devDependencies": {
        "@types/mocha": "^9.0.0",
@@ -23,14 +24,14 @@
        "nyc": "^15.1.0",
        "prettier": "^2.3.2",
        "rimraf": "^3.0.2",
-        "socket.io-client": "4.5.4",
+        "socket.io-client": "4.7.0",
        "socket.io-client-v2": "npm:socket.io-client@^2.4.0",
        "superagent": "^8.0.0",
        "supertest": "^6.1.6",
        "ts-node": "^10.2.1",
        "tsd": "^0.21.0",
        "typescript": "^4.4.2",
-        "uWebSockets.js": "github:uNetworking/uWebSockets.js#v20.0.0"
+        "uWebSockets.js": "github:uNetworking/uWebSockets.js#v20.30.0"
      },
      "engines": {
        "node": ">=10.0.0"
@@ -1228,9 +1229,9 @@
      }
    },
    "node_modules/cookiejar": {
-      "version": "2.1.3",
-      "resolved": "https://registry.npmjs.org/cookiejar/-/cookiejar-2.1.3.tgz",
-      "integrity": "sha512-JxbCBUdrfr6AQjOXrxoTvAMJO4HBTUIlBzslcJPAz+/KT8yk53fXun51u+RenNYvad/+Vc2DIz5o9UxlCDymFQ==",
+      "version": "2.1.4",
+      "resolved": "https://registry.npmjs.org/cookiejar/-/cookiejar-2.1.4.tgz",
+      "integrity": "sha512-LDx6oHrK+PhzLKJU9j5S7/Y3jM/mUHvD/DeI1WQmJn652iPC5Y4TBzC9l+5OMOXlyTTA+SmVUPm0HQUwpD5Jqw==",
      "dev": true
    },
    "node_modules/cors": {
@@ -1377,9 +1378,9 @@
      "dev": true
    },
    "node_modules/engine.io": {
-      "version": "6.3.1",
-      "resolved": "https://registry.npmjs.org/engine.io/-/engine.io-6.3.1.tgz",
-      "integrity": "sha512-VhEArSKyCC8dv223fltbMOqaJInFZqIqLABLnD3VLhclriF9sxnAJu6ZvnIMI+p7+ByZBxXd4otTrLAeeMTImg==",
+      "version": "6.5.0",
+      "resolved": "https://registry.npmjs.org/engine.io/-/engine.io-6.5.0.tgz",
+      "integrity": "sha512-UlfoK1iD62Hkedw2TmuHdhDsZCGaAyp+LZ/AvnImjYBeWagA3qIEETum90d6shMeFZiDuGT66zVCdx1wKYKGGg==",
      "dependencies": {
        "@types/cookie": "^0.4.1",
        "@types/cors": "^2.8.12",
@@ -1389,7 +1390,7 @@
        "cookie": "~0.4.1",
        "cors": "~2.8.5",
        "debug": "~4.3.1",
-        "engine.io-parser": "~5.0.3",
+        "engine.io-parser": "~5.1.0",
        "ws": "~8.11.0"
      },
      "engines": {
@@ -1397,46 +1398,26 @@
      }
    },
    "node_modules/engine.io-client": {
-      "version": "6.2.3",
-      "resolved": "https://registry.npmjs.org/engine.io-client/-/engine.io-client-6.2.3.tgz",
-      "integrity": "sha512-aXPtgF1JS3RuuKcpSrBtimSjYvrbhKW9froICH4s0F3XQWLxsKNxqzG39nnvQZQnva4CMvUK63T7shevxRyYHw==",
+      "version": "6.5.0",
+      "resolved": "https://registry.npmjs.org/engine.io-client/-/engine.io-client-6.5.0.tgz",
+      "integrity": "sha512-C7eN3OKggSfd5g8IDgUA9guC8TNS6CEganKT7dL6Fp3q+FobcQ/WBn2Qq2XTL1vNTiFZfDzXohvqLuR9dWejdg==",
      "dev": true,
      "dependencies": {
        "@socket.io/component-emitter": "~3.1.0",
        "debug": "~4.3.1",
-        "engine.io-parser": "~5.0.3",
-        "ws": "~8.2.3",
+        "engine.io-parser": "~5.1.0",
+        "ws": "~8.11.0",
        "xmlhttprequest-ssl": "~2.0.0"
      }
    },
    "node_modules/engine.io-parser": {
-      "version": "5.0.4",
-      "resolved": "https://registry.npmjs.org/engine.io-parser/-/engine.io-parser-5.0.4.tgz",
-      "integrity": "sha512-+nVFp+5z1E3HcToEnO7ZIj3g+3k9389DvWtvJZz0T6/eOCPIyyxehFcedoYrZQrp0LgQbD9pPXhpMBKMd5QURg==",
+      "version": "5.1.0",
+      "resolved": "https://registry.npmjs.org/engine.io-parser/-/engine.io-parser-5.1.0.tgz",
+      "integrity": "sha512-enySgNiK5tyZFynt3z7iqBR+Bto9EVVVvDFuTT0ioHCGbzirZVGDGiQjZzEp8hWl6hd5FSVytJGuScX1C1C35w==",
      "engines": {
        "node": ">=10.0.0"
      }
    },
-    "node_modules/engine.io/node_modules/ws": {
-      "version": "8.11.0",
-      "resolved": "https://registry.npmjs.org/ws/-/ws-8.11.0.tgz",
-      "integrity": "sha512-HPG3wQd9sNQoT9xHyNCXoDUa+Xw/VevmY9FoHyQ+g+rrMn4j6FB4np7Z0OhdTgjx6MgQLK7jwSy1YecU1+4Asg==",
-      "engines": {
-        "node": ">=10.0.0"
-      },
-      "peerDependencies": {
-        "bufferutil": "^4.0.1",
-        "utf-8-validate": "^5.0.2"
-      },
-      "peerDependenciesMeta": {
-        "bufferutil": {
-          "optional": true
-        },
-        "utf-8-validate": {
-          "optional": true
-        }
-      }
-    },
    "node_modules/error-ex": {
      "version": "1.3.2",
      "resolved": "https://registry.npmjs.org/error-ex/-/error-ex-1.3.2.tgz",
@@ -3482,36 +3463,16 @@
        "ws": "~8.11.0"
      }
    },
-    "node_modules/socket.io-adapter/node_modules/ws": {
-      "version": "8.11.0",
-      "resolved": "https://registry.npmjs.org/ws/-/ws-8.11.0.tgz",
-      "integrity": "sha512-HPG3wQd9sNQoT9xHyNCXoDUa+Xw/VevmY9FoHyQ+g+rrMn4j6FB4np7Z0OhdTgjx6MgQLK7jwSy1YecU1+4Asg==",
-      "engines": {
-        "node": ">=10.0.0"
-      },
-      "peerDependencies": {
-        "bufferutil": "^4.0.1",
-        "utf-8-validate": "^5.0.2"
-      },
-      "peerDependenciesMeta": {
-        "bufferutil": {
-          "optional": true
-        },
-        "utf-8-validate": {
-          "optional": true
-        }
-      }
-    },
    "node_modules/socket.io-client": {
-      "version": "4.5.4",
-      "resolved": "https://registry.npmjs.org/socket.io-client/-/socket.io-client-4.5.4.tgz",
-      "integrity": "sha512-ZpKteoA06RzkD32IbqILZ+Cnst4xewU7ZYK12aS1mzHftFFjpoMz69IuhP/nL25pJfao/amoPI527KnuhFm01g==",
+      "version": "4.7.0",
+      "resolved": "https://registry.npmjs.org/socket.io-client/-/socket.io-client-4.7.0.tgz",
+      "integrity": "sha512-7Q8CeDrhuZzg4QLXl3tXlk5yb086oxYzehAVZRLiGCzCmtDneiHz1qHyyWcxhTgxXiokVpWQXoG/u60HoXSQew==",
      "dev": true,
      "dependencies": {
        "@socket.io/component-emitter": "~3.1.0",
        "debug": "~4.3.2",
-        "engine.io-client": "~6.2.3",
-        "socket.io-parser": "~4.2.1"
+        "engine.io-client": "~6.5.0",
+        "socket.io-parser": "~4.2.4"
      },
      "engines": {
        "node": ">=10.0.0"
@@ -3626,9 +3587,9 @@
      }
    },
    "node_modules/socket.io-parser": {
-      "version": "4.2.2",
-      "resolved": "https://registry.npmjs.org/socket.io-parser/-/socket.io-parser-4.2.2.tgz",
-      "integrity": "sha512-DJtziuKypFkMMHCm2uIshOYC7QaylbtzQwiMYDuCKy3OPkjLzu4B2vAhTlqipRHHzrI0NJeBAizTK7X+6m1jVw==",
+      "version": "4.2.4",
+      "resolved": "https://registry.npmjs.org/socket.io-parser/-/socket.io-parser-4.2.4.tgz",
+      "integrity": "sha512-/GbIKmo8ioc+NIWIhwdecY0ge+qVBSMdgxGygevmdHj24bsfgtCmcUUcQ5ZzcylGFHsN3k4HB4Cgkl96KVnuew==",
      "dependencies": {
        "@socket.io/component-emitter": "~3.1.0",
        "debug": "~4.3.1"
@@ -4145,8 +4106,8 @@
      }
    },
    "node_modules/uWebSockets.js": {
-      "version": "20.0.0",
-      "resolved": "git+https://git@github.com/uNetworking/uWebSockets.js.git#4558ee00f9f1f686fffe1accbfc2e85b1af9c50f",
+      "version": "20.30.0",
+      "resolved": "git+https://git@github.com/uNetworking/uWebSockets.js.git#d39d4181daf5b670d44cbc1b18f8c28c85fd4142",
      "dev": true
    },
    "node_modules/v8-compile-cache-lib": {
@@ -4236,10 +4197,9 @@
      }
    },
    "node_modules/ws": {
-      "version": "8.2.3",
-      "resolved": "https://registry.npmjs.org/ws/-/ws-8.2.3.tgz",
-      "integrity": "sha512-wBuoj1BDpC6ZQ1B7DWQBYVLphPWkm8i9Y0/3YdHjHKHiohOJ1ws+3OccDWtH+PoC9DZD5WOTrJvNbWvjS6JWaA==",
-      "dev": true,
+      "version": "8.11.0",
+      "resolved": "https://registry.npmjs.org/ws/-/ws-8.11.0.tgz",
+      "integrity": "sha512-HPG3wQd9sNQoT9xHyNCXoDUa+Xw/VevmY9FoHyQ+g+rrMn4j6FB4np7Z0OhdTgjx6MgQLK7jwSy1YecU1+4Asg==",
      "engines": {
        "node": ">=10.0.0"
      },
@@ -5312,9 +5272,9 @@
      "integrity": "sha512-aSWTXFzaKWkvHO1Ny/s+ePFpvKsPnjc551iI41v3ny/ow6tBG5Vd+FuqGNhh1LxOmVzOlGUriIlOaokOvhaStA=="
    },
    "cookiejar": {
-      "version": "2.1.3",
-      "resolved": "https://registry.npmjs.org/cookiejar/-/cookiejar-2.1.3.tgz",
-      "integrity": "sha512-JxbCBUdrfr6AQjOXrxoTvAMJO4HBTUIlBzslcJPAz+/KT8yk53fXun51u+RenNYvad/+Vc2DIz5o9UxlCDymFQ==",
+      "version": "2.1.4",
+      "resolved": "https://registry.npmjs.org/cookiejar/-/cookiejar-2.1.4.tgz",
+      "integrity": "sha512-LDx6oHrK+PhzLKJU9j5S7/Y3jM/mUHvD/DeI1WQmJn652iPC5Y4TBzC9l+5OMOXlyTTA+SmVUPm0HQUwpD5Jqw==",
      "dev": true
    },
    "cors": {
@@ -5428,9 +5388,9 @@
      "dev": true
    },
    "engine.io": {
-      "version": "6.3.1",
-      "resolved": "https://registry.npmjs.org/engine.io/-/engine.io-6.3.1.tgz",
-      "integrity": "sha512-VhEArSKyCC8dv223fltbMOqaJInFZqIqLABLnD3VLhclriF9sxnAJu6ZvnIMI+p7+ByZBxXd4otTrLAeeMTImg==",
+      "version": "6.5.0",
+      "resolved": "https://registry.npmjs.org/engine.io/-/engine.io-6.5.0.tgz",
+      "integrity": "sha512-UlfoK1iD62Hkedw2TmuHdhDsZCGaAyp+LZ/AvnImjYBeWagA3qIEETum90d6shMeFZiDuGT66zVCdx1wKYKGGg==",
      "requires": {
        "@types/cookie": "^0.4.1",
        "@types/cors": "^2.8.12",
@@ -5440,35 +5400,27 @@
        "cookie": "~0.4.1",
        "cors": "~2.8.5",
        "debug": "~4.3.1",
-        "engine.io-parser": "~5.0.3",
+        "engine.io-parser": "~5.1.0",
        "ws": "~8.11.0"
-      },
-      "dependencies": {
-        "ws": {
-          "version": "8.11.0",
-          "resolved": "https://registry.npmjs.org/ws/-/ws-8.11.0.tgz",
-          "integrity": "sha512-HPG3wQd9sNQoT9xHyNCXoDUa+Xw/VevmY9FoHyQ+g+rrMn4j6FB4np7Z0OhdTgjx6MgQLK7jwSy1YecU1+4Asg==",
-          "requires": {}
-        }
      }
    },
    "engine.io-client": {
-      "version": "6.2.3",
-      "resolved": "https://registry.npmjs.org/engine.io-client/-/engine.io-client-6.2.3.tgz",
-      "integrity": "sha512-aXPtgF1JS3RuuKcpSrBtimSjYvrbhKW9froICH4s0F3XQWLxsKNxqzG39nnvQZQnva4CMvUK63T7shevxRyYHw==",
+      "version": "6.5.0",
+      "resolved": "https://registry.npmjs.org/engine.io-client/-/engine.io-client-6.5.0.tgz",
+      "integrity": "sha512-C7eN3OKggSfd5g8IDgUA9guC8TNS6CEganKT7dL6Fp3q+FobcQ/WBn2Qq2XTL1vNTiFZfDzXohvqLuR9dWejdg==",
      "dev": true,
      "requires": {
        "@socket.io/component-emitter": "~3.1.0",
        "debug": "~4.3.1",
-        "engine.io-parser": "~5.0.3",
-        "ws": "~8.2.3",
+        "engine.io-parser": "~5.1.0",
+        "ws": "~8.11.0",
        "xmlhttprequest-ssl": "~2.0.0"
      }
    },
    "engine.io-parser": {
-      "version": "5.0.4",
-      "resolved": "https://registry.npmjs.org/engine.io-parser/-/engine.io-parser-5.0.4.tgz",
-      "integrity": "sha512-+nVFp+5z1E3HcToEnO7ZIj3g+3k9389DvWtvJZz0T6/eOCPIyyxehFcedoYrZQrp0LgQbD9pPXhpMBKMd5QURg=="
+      "version": "5.1.0",
+      "resolved": "https://registry.npmjs.org/engine.io-parser/-/engine.io-parser-5.1.0.tgz",
+      "integrity": "sha512-enySgNiK5tyZFynt3z7iqBR+Bto9EVVVvDFuTT0ioHCGbzirZVGDGiQjZzEp8hWl6hd5FSVytJGuScX1C1C35w=="
    },
    "error-ex": {
      "version": "1.3.2",
@@ -6968,26 +6920,18 @@
      "integrity": "sha512-87C3LO/NOMc+eMcpcxUBebGjkpMDkNBS9tf7KJqcDsmL936EChtVva71Dw2q4tQcuVC+hAUy4an2NO/sYXmwRA==",
      "requires": {
        "ws": "~8.11.0"
-      },
-      "dependencies": {
-        "ws": {
-          "version": "8.11.0",
-          "resolved": "https://registry.npmjs.org/ws/-/ws-8.11.0.tgz",
-          "integrity": "sha512-HPG3wQd9sNQoT9xHyNCXoDUa+Xw/VevmY9FoHyQ+g+rrMn4j6FB4np7Z0OhdTgjx6MgQLK7jwSy1YecU1+4Asg==",
-          "requires": {}
-        }
      }
    },
    "socket.io-client": {
-      "version": "4.5.4",
-      "resolved": "https://registry.npmjs.org/socket.io-client/-/socket.io-client-4.5.4.tgz",
-      "integrity": "sha512-ZpKteoA06RzkD32IbqILZ+Cnst4xewU7ZYK12aS1mzHftFFjpoMz69IuhP/nL25pJfao/amoPI527KnuhFm01g==",
+      "version": "4.7.0",
+      "resolved": "https://registry.npmjs.org/socket.io-client/-/socket.io-client-4.7.0.tgz",
+      "integrity": "sha512-7Q8CeDrhuZzg4QLXl3tXlk5yb086oxYzehAVZRLiGCzCmtDneiHz1qHyyWcxhTgxXiokVpWQXoG/u60HoXSQew==",
      "dev": true,
      "requires": {
        "@socket.io/component-emitter": "~3.1.0",
        "debug": "~4.3.2",
-        "engine.io-client": "~6.2.3",
-        "socket.io-parser": "~4.2.1"
+        "engine.io-client": "~6.5.0",
+        "socket.io-parser": "~4.2.4"
      }
    },
    "socket.io-client-v2": {
@@ -7083,9 +7027,9 @@
      }
    },
    "socket.io-parser": {
-      "version": "4.2.2",
-      "resolved": "https://registry.npmjs.org/socket.io-parser/-/socket.io-parser-4.2.2.tgz",
-      "integrity": "sha512-DJtziuKypFkMMHCm2uIshOYC7QaylbtzQwiMYDuCKy3OPkjLzu4B2vAhTlqipRHHzrI0NJeBAizTK7X+6m1jVw==",
+      "version": "4.2.4",
+      "resolved": "https://registry.npmjs.org/socket.io-parser/-/socket.io-parser-4.2.4.tgz",
+      "integrity": "sha512-/GbIKmo8ioc+NIWIhwdecY0ge+qVBSMdgxGygevmdHj24bsfgtCmcUUcQ5ZzcylGFHsN3k4HB4Cgkl96KVnuew==",
      "requires": {
        "@socket.io/component-emitter": "~3.1.0",
        "debug": "~4.3.1"
@@ -7459,9 +7403,9 @@
      "dev": true
    },
    "uWebSockets.js": {
-      "version": "git+https://git@github.com/uNetworking/uWebSockets.js.git#4558ee00f9f1f686fffe1accbfc2e85b1af9c50f",
+      "version": "git+https://git@github.com/uNetworking/uWebSockets.js.git#d39d4181daf5b670d44cbc1b18f8c28c85fd4142",
      "dev": true,
-      "from": "uWebSockets.js@github:uNetworking/uWebSockets.js#v20.0.0"
+      "from": "uWebSockets.js@github:uNetworking/uWebSockets.js#v20.30.0"
    },
    "v8-compile-cache-lib": {
      "version": "3.0.1",
@@ -7535,10 +7479,9 @@
      }
    },
    "ws": {
-      "version": "8.2.3",
-      "resolved": "https://registry.npmjs.org/ws/-/ws-8.2.3.tgz",
-      "integrity": "sha512-wBuoj1BDpC6ZQ1B7DWQBYVLphPWkm8i9Y0/3YdHjHKHiohOJ1ws+3OccDWtH+PoC9DZD5WOTrJvNbWvjS6JWaA==",
-      "dev": true,
+      "version": "8.11.0",
+      "resolved": "https://registry.npmjs.org/ws/-/ws-8.11.0.tgz",
+      "integrity": "sha512-HPG3wQd9sNQoT9xHyNCXoDUa+Xw/VevmY9FoHyQ+g+rrMn4j6FB4np7Z0OhdTgjx6MgQLK7jwSy1YecU1+4Asg==",
      "requires": {}
    },
    "xmlhttprequest-ssl": {
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
  "name": "socket.io",
-  "version": "4.5.4",
+  "version": "4.7.0",
  "description": "node.js realtime framework server",
  "keywords": [
    "realtime",
@@ -26,9 +26,9 @@
  "type": "commonjs",
  "main": "./dist/index.js",
  "exports": {
+    "types": "./dist/index.d.ts",
    "import": "./wrapper.mjs",
-    "require": "./dist/index.js",
-    "types": "./dist/index.d.ts"
+    "require": "./dist/index.js"
  },
  "types": "./dist/index.d.ts",
  "license": "MIT",
@@ -48,10 +48,11 @@
  "dependencies": {
    "accepts": "~1.3.4",
    "base64id": "~2.0.0",
+    "cors": "~2.8.5",
    "debug": "~4.3.2",
-    "engine.io": "~6.3.1",
+    "engine.io": "~6.5.0",
    "socket.io-adapter": "~2.5.2",
-    "socket.io-parser": "~4.2.1"
+    "socket.io-parser": "~4.2.4"
  },
  "devDependencies": {
    "@types/mocha": "^9.0.0",
@@ -60,14 +61,14 @@
    "nyc": "^15.1.0",
    "prettier": "^2.3.2",
    "rimraf": "^3.0.2",
-    "socket.io-client": "4.5.4",
+    "socket.io-client": "4.7.0",
    "socket.io-client-v2": "npm:socket.io-client@^2.4.0",
    "superagent": "^8.0.0",
    "supertest": "^6.1.6",
    "ts-node": "^10.2.1",
    "tsd": "^0.21.0",
    "typescript": "^4.4.2",
-    "uWebSockets.js": "github:uNetworking/uWebSockets.js#v20.0.0"
+    "uWebSockets.js": "github:uNetworking/uWebSockets.js#v20.30.0"
  },
  "contributors": [
    {
--- a/test/connection-state-recovery.ts
+++ b/test/connection-state-recovery.ts
@@ -2,6 +2,7 @@ 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
@@ -193,4 +194,54 @@ describe("connection state recovery", () => {

    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();
+  });
 });
--- a/test/namespaces.ts
+++ b/test/namespaces.ts
@@ -652,5 +652,16 @@ describe("namespaces", () => {

      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();
+    });
  });
 });
--- a/test/server-attachment.ts
+++ b/test/server-attachment.ts
@@ -70,6 +70,27 @@ describe("server attachment", () => {
        });
    });

+    it("should serve client with necessary CORS headers", (done) => {
+      const srv = createServer();
+      new Server(srv, {
+        cors: {
+          origin: "https://good-origin.com",
+        },
+      });
+      request(srv)
+        .get("/socket.io/socket.io.js")
+        .set("origin", "https://good-origin.com")
+        .buffer(true)
+        .end((err, res) => {
+          if (err) return done(err);
+          expect(res.headers["access-control-allow-origin"]).to.be(
+            "https://good-origin.com"
+          );
+          expect(res.status).to.be(200);
+          done();
+        });
+    });
+
    it(
      "should serve bundle with msgpack parser",
      testSource("socket.io.msgpack.min.js")
--- a/test/socket.ts
+++ b/test/socket.ts
@@ -852,10 +852,6 @@ describe("socket", () => {
  it("should not crash when messing with Object prototype (and other globals)", (done) => {
    // @ts-ignore
    Object.prototype.foo = "bar";
-    // @ts-ignore
-    global.File = "";
-    // @ts-ignore
-    global.Blob = [];
    const io = new Server(0);
    const socket = createClient(io);

--- a/test/uws.ts
+++ b/test/uws.ts
@@ -53,7 +53,7 @@ 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);
  });
Author	SHA1	Message	Date
Damien Arrachequesne	00d8ee5b05	chore(release): 4.7.0 Diff: https://github.com/socketio/socket.io/compare/4.6.2...4.7.0	2023-06-22 11:27:45 +02:00
Damien Arrachequesne	2dd5fa9dd4	ci: add Node.js 20 in the test matrix Reference: https://github.com/nodejs/Release	2023-06-22 07:55:32 +02:00
Damien Arrachequesne	a5dff0ac83	docs(examples): increase httpd ProxyTimeout value (2)	2023-06-21 00:07:44 +02:00
Damien Arrachequesne	3035c25982	docs(examples): increase httpd ProxyTimeout value With a value that is too small, the HTTP long-polling request receives an HTTP 502 response code and the connection gets closed.	2023-06-20 23:57:46 +02:00
Damien Arrachequesne	63f181cc12	feat: serve client bundles with CORS headers The version of the `cors` package matches the one used by `engine.io`. Related: https://github.com/socketio/socket.io/issues/3552	2023-06-20 14:32:59 +02:00
Damien Arrachequesne	a250e283da	chore: bump engine.io to version 6.5.0 Diff: https://github.com/socketio/engine.io/compare/6.4.2...6.5.0 Release notes: https://github.com/socketio/engine.io/releases/tag/6.5.0	2023-06-20 09:17:10 +02:00
SyedTayyabUlMazhar	e5c62cad60	fix: remove the Partial modifier from the socket.data type (#4740 ) Wrapping SocketData with Partial causes issues when reading data even if you've made sure to pass all values. If someone want to make their type Partial or make only a few properties optional, they can do so in their own type instead. Related: https://github.com/socketio/socket.io/issues/4537	2023-06-20 07:49:02 +02:00
Damien Arrachequesne	01d37624a8	docs(changelog): update the version range of the engine.io dependency	2023-05-31 11:28:00 +02:00
Damien Arrachequesne	faf914c9ab	chore(release): 4.6.2 Diff: https://github.com/socketio/socket.io/compare/4.6.1...4.6.2	2023-05-31 11:15:41 +02:00
Damien Arrachequesne	15af22fc22	refactor: add a noop handler for the error event We should reduce the scope of the "event" error in the next major version, as it is overloaded today: - it can be sent by the client (`socket.emit("error")`, which is a perfectly valid event name) - it can be emitted when the connection encounters an error (an invalid packet for example) - it can be emitted when a packet is rejected in a middleware (`socket.use()`) Related: https://github.com/socketio/socket.io/issues/2047	2023-05-24 10:47:52 +02:00
Damien Arrachequesne	d3658944e5	chore: bump socket.io-parser to version 4.2.3 Reference: https://github.com/advisories/GHSA-cqmj-92xf-r6r9	2023-05-24 07:27:12 +02:00
Damien Arrachequesne	12b0de4f52	chore: bump engine.io to version 6.4.2 Reference: https://github.com/advisories/GHSA-q9mw-68c2-j6m5 Related: https://github.com/socketio/socket.io/issues/4711	2023-05-10 10:20:42 +02:00
Mateusz Burzyński	3d44aae381	fix(exports): move `types` condition to the top (#4698 ) Related: https://github.com/microsoft/TypeScript/issues/50762	2023-05-04 07:27:09 +02:00
Damien Arrachequesne	cbf0362476	docs(examples): bump dependencies for the private messaging example Related: https://github.com/socketio/socket.io/issues/4681	2023-05-02 18:07:07 +02:00
Damien Arrachequesne	59280da20b	docs(examples): update examples to docker compose v2 Reference: https://docs.docker.com/compose/ Related: https://github.com/socketio/socket.io/discussions/4669	2023-04-07 15:57:20 +02:00
Damien Arrachequesne	50a4d37cb8	docs(changelog): add version of transitive dependencies	2023-03-27 17:35:42 +02:00
Damien Arrachequesne	6458b2bef1	docs(example): basic WebSocket-only client	2023-03-24 11:17:29 +01:00
Damien Arrachequesne	b56da8a99f	docs(examples): upgrade to React 18 Reference: https://reactjs.org/blog/2022/03/08/react-18-upgrade-guide.html	2023-03-07 08:31:21 +01:00
Damien Arrachequesne	7952312911	chore(release): 4.6.1 Diff: https://github.com/socketio/socket.io/compare/4.6.0...4.6.1	2023-02-20 17:49:41 +01:00
Damien Arrachequesne	0d0a7a22b5	fix: properly handle manually created dynamic namespaces Namespaces that match the regex of a parent namespace will now be added as a child of this namespace: ```js const parentNamespace = io.of(/^\/dynamic-\d+$/); const childNamespace = io.of("/dynamic-101"); ``` Related: - https://github.com/socketio/socket.io/issues/4615 - https://github.com/socketio/socket.io/issues/4164 - https://github.com/socketio/socket.io/issues/4015 - https://github.com/socketio/socket.io/issues/3960	2023-02-20 01:19:01 +01:00
Damien Arrachequesne	2a8565fd1e	refactor: catch errors when trying to restore the connection state	2023-02-20 01:18:08 +01:00
Igor Lins e Silva	d0b22c6302	fix(types): fix nodenext module resolution compatibility (#4625 ) The import added in [1] was invalid, because it used an non-exported class. Related: https://github.com/socketio/socket.io/issues/4621 [1]: `d4a9b2cdcb`	2023-02-20 01:15:35 +01:00
Nabaraj Subedi	e71f3d7dbe	docs: minor style fix (#4619 )	2023-02-16 09:25:43 +01:00
Damien Arrachequesne	a2e5d1f77f	chore(release): 4.6.0 Diff: https://github.com/socketio/socket.io/compare/4.5.4...4.6.0	2023-02-07 01:07:46 +01:00
Damien Arrachequesne	d8143cc067	refactor: do not persist session if connection state recovery if disabled This is a follow-up commit of [1]. Without it, adapter.persistSession() would be called even if the connection state recovery feature was disabled. [1]: `54d5ee05a6`	2023-02-06 18:03:34 +01:00
Damien Arrachequesne	b2dd7cf660	chore: bump engine.io to version 6.4.0 Diff: https://github.com/socketio/engine.io/compare/6.3.1...6.4.0 Release notes: https://github.com/socketio/engine.io/releases/tag/6.4.0	2023-02-06 17:43:02 +01:00
Damien Arrachequesne	3734b74b45	revert: feat: expose current offset to allow deduplication This reverts commit `4e64123862`. Using the id of the socket is not possible, since it is lost upon reconnection (unless connection recovery is successful), so we revert the previous change.	2023-02-06 17:36:37 +01:00
Edouard Benauw	8aa94991ce	feat: add description to the disconnecting and disconnect events (#4622 ) See also: `b862924b7f`	2023-02-04 09:03:01 +01:00
Damien Arrachequesne	4e64123862	feat: expose current offset to allow deduplication Related: `655dce9755`	2023-02-04 08:56:55 +01:00
Damien Arrachequesne	115a9819fd	refactor: do not include the pid by default So that the client knows whether the connection state recovery feature is enabled. See also: `54d5ee05a6`	2023-01-25 09:39:22 +01:00
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				class e{#e=new Map;on(e,t){let s=this.#e.get(e);s\|\|this.#e.set(e,s=[]),s.push(t)}emit(e,...t){const s=this.#e.get(e);if(s)for(const e of s)e.apply(null,t)}}const t="0",s="1",n="2",i="3",o="4",r={CONNECT:0,DISCONNECT:1,EVENT:2};function c(){}class a extends e{id;connected=!1;#t;#s;#n;#i;#o;#r=[];#c;#a=!0;constructor(e,t){super(),this.#t=e,this.#s=Object.assign({path:"/socket.io/",reconnectionDelay:2e3},t),this.#h()}#h(){this.#n=new WebSocket(this.#u()),this.#n.onmessage=({data:e})=>this.#p(e),this.#n.onerror=c,this.#n.onclose=()=>this.#l("transport close")}#u(){return`${this.#t.replace(/^http/,"ws")}${this.#s.path}?EIO=4&transport=websocket`}#p(e){if("string"==typeof e)switch(e[0]){case t:this.#d(e);break;case s:this.#l("transport close");break;case n:this.#T(),this.#m(i);break;case o:let c;try{c=function(e){let t=1;const s={type:parseInt(e.charAt(t++),10)};e.charAt(t)&&(s.data=JSON.parse(e.substring(t)));if(!function(e){switch(e.type){case r.CONNECT:return"object"==typeof e.data;case r.DISCONNECT:return void 0===e.data;case r.EVENT:{const t=e.data;return Array.isArray(t)&&t.length>0&&"string"==typeof t[0]}default:return!1}}(s))throw new Error("invalid format");return s}(e)}catch(e){return this.#l("parse error")}this.#f(c);break;default:this.#l("parse error")}}#d(e){let t;try{t=JSON.parse(e.substring(1))}catch(e){return this.#l("parse error")}this.#o=t.pingInterval+t.pingTimeout,this.#T(),this.#C()}#f(e){switch(e.type){case r.CONNECT:this.#g(e);break;case r.DISCONNECT:this.#a=!1,this.#l("io server disconnect");break;case r.EVENT:super.emit.apply(this,e.data);break;default:this.#l("parse error")}}#g(e){this.id=e.data.sid,this.connected=!0,this.#r.forEach((e=>this.#y(e))),this.#r.slice(0),super.emit("connect")}#l(e){this.#n&&(this.#n.onclose=c,this.#n.close()),clearTimeout(this.#i),clearTimeout(this.#c),this.connected?(this.connected=!1,this.id=void 0,super.emit("disconnect",e)):super.emit("connect_error",e),this.#a&&(this.#c=setTimeout((()=>this.#h()),this.#s.reconnectionDelay))}#T(){clearTimeout(this.#i),this.#i=setTimeout((()=>{this.#l("ping timeout")}),this.#o)}#m(e){this.#n.readyState===WebSocket.OPEN&&this.#n.send(e)}#y(e){this.#m(o+function(e){let t=""+e.type;e.data&&(t+=JSON.stringify(e.data));return t}(e))}#C(){this.#y({type:r.CONNECT})}emit(...e){const t={type:r.EVENT,data:e};this.connected?this.#y(t):this.#r.push(t)}disconnect(){this.#a=!1,this.#l("io client disconnect")}}function h(e,t){return"string"!=typeof e&&(t=e,e=location.origin),new a(e,t)}export{h as io};