chore(release): 3.1.2

Diff: https://github.com/socketio/socket.io/compare/3.1.1...3.1.2
fix: ignore packet received after disconnection
2026-01-11 16:08:24 -05:00 · 2021-02-26 01:18:42 +01:00 · 2021-02-26 00:58:30 +01:00 · 2021-02-26 00:58:01 +01:00 · 2021-02-17 00:24:23 +01:00 · 2021-02-17 00:22:55 +01:00
59 changed files with 1870 additions and 356 deletions
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,7 +12,7 @@ jobs:

    strategy:
      matrix:
-        node-version: [10.x, 12.x, 14.x]
+        node-version: [10.x, 12.x, 14.x, 15.x]

    steps:
      - uses: actions/checkout@v2
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,21 @@
+## [3.1.2](https://github.com/socketio/socket.io/compare/3.1.1...3.1.2) (2021-02-26)
+
+
+### Bug Fixes
+
+* ignore packets received after disconnection ([494c64e](https://github.com/socketio/socket.io/commit/494c64e44f645cbd24c645f1186d203789e84af0))
+
+
+## [3.1.1](https://github.com/socketio/socket.io/compare/3.1.0...3.1.1) (2021-02-03)
+
+
+### Bug Fixes
+
+* properly parse the CONNECT packet in v2 compatibility mode ([6f4bd7f](https://github.com/socketio/socket.io/commit/6f4bd7f8e7c41a075a8014565330a77c38b03a8d))
+* **typings:** add return types and general-case overload signatures ([#3776](https://github.com/socketio/socket.io/issues/3776)) ([9e8f288](https://github.com/socketio/socket.io/commit/9e8f288ca9f14f91064b8d3cce5946f7d23d407c))
+* **typings:** update the types of "query", "auth" and "headers" ([4f2e9a7](https://github.com/socketio/socket.io/commit/4f2e9a716d9835b550c8fd9a9b429ebf069c2895))
+
+
 # [3.1.0](https://github.com/socketio/socket.io/compare/3.0.5...3.1.0) (2021-01-15)


--- a/Readme.md
+++ b/Readme.md
@@ -36,7 +36,7 @@ For this purpose, it relies on [Engine.IO](https://github.com/socketio/engine.io

 #### Auto-reconnection support

-Unless instructed otherwise a disconnected client will try to reconnect forever, until the server is available again. Please see the available reconnection options [here](https://github.com/socketio/socket.io-client/blob/master/docs/API.md#new-managerurl-options).
+Unless instructed otherwise a disconnected client will try to reconnect forever, until the server is available again. Please see the available reconnection options [here](https://socket.io/docs/v3/client-api/#new-Manager-url-options).

 #### Disconnection detection

@@ -85,7 +85,11 @@ This is a useful feature to send notifications to a group of users, or to a give
 ## Installation

 ```bash
+// with npm
 npm install socket.io
+
+// with yarn
+yarn add socket.io
 ```

 ## How to use
--- a/client-dist/socket.io.js
+++ b/client-dist/socket.io.js
@@ -1,5 +1,5 @@
 /*!
- * Socket.IO v3.1.0
+ * Socket.IO v3.1.2
 * (c) 2014-2021 Guillermo Rauch
 * Released under the MIT License.
 */
@@ -12,7 +12,7 @@
 		exports["io"] = factory();
 	else
 		root["io"] = factory();
-})(window, function() {
+})(this, function() {
 return /******/ (function(modules) { // webpackBootstrap
 /******/ 	// The module cache
 /******/ 	var installedModules = {};
@@ -151,7 +151,7 @@ function lookup(uri, opts) {
  }

  opts = opts || {};
-  var parsed = url_1.url(uri);
+  var parsed = url_1.url(uri, opts.path);
  var source = parsed.source;
  var id = parsed.id;
  var path = parsed.path;
@@ -172,7 +172,7 @@ function lookup(uri, opts) {
  }

  if (parsed.query && !opts.query) {
-    opts.query = parsed.query;
+    opts.query = parsed.queryKey;
  }

  return io.socket(parsed.path, opts);
@@ -592,7 +592,6 @@ var Manager = /*#__PURE__*/function (_Emitter) {
    key: "_packet",
    value: function _packet(packet) {
      debug("writing packet %j", packet);
-      if (packet.query && packet.type === 0) packet.nsp += "?" + packet.query;
      var encodedPackets = this.encoder.encode(packet);

      for (var i = 0; i < encodedPackets.length; i++) {
@@ -1458,13 +1457,16 @@ var debug = __webpack_require__(/*! debug */ "./node_modules/debug/src/browser.j
 * URL parser.
 *
 * @param uri - url
+ * @param path - the request path of the connection
 * @param loc - An object meant to mimic window.location.
 *        Defaults to window.location.
 * @public
 */


-function url(uri, loc) {
+function url(uri) {
+  var path = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : "";
+  var loc = arguments.length > 2 ? arguments[2] : undefined;
  var obj = uri; // default to window.location

  loc = loc || typeof location !== "undefined" && location;
@@ -1507,7 +1509,7 @@ function url(uri, loc) {
  var ipv6 = obj.host.indexOf(":") !== -1;
  var host = ipv6 ? "[" + obj.host + "]" : obj.host; // define unique id

-  obj.id = obj.protocol + "://" + host + ":" + obj.port; // define href
+  obj.id = obj.protocol + "://" + host + ":" + obj.port + path; // define href

  obj.href = obj.protocol + "://" + host + (loc && loc.port === obj.port ? "" : ":" + obj.port);
  return obj;
@@ -1797,7 +1799,7 @@ Emitter.prototype.hasListeners = function (event) {
 /*! no static exports found */
 /***/ (function(module, exports, __webpack_require__) {

-/* WEBPACK VAR INJECTION */(function(process) {/* eslint-env browser */
+/* eslint-env browser */

 /**
 * This is the web browser implementation of `debug()`.
@@ -1978,7 +1980,6 @@ formatters.j = function (v) {
    return '[UnexpectedJSONParseError]: ' + error.message;
  }
 };
-/* WEBPACK VAR INJECTION */}.call(this, __webpack_require__(/*! ./../../process/browser.js */ "./node_modules/process/browser.js")))

 /***/ }),

@@ -2432,6 +2433,17 @@ var Socket = /*#__PURE__*/function (_Emitter) {

    _this.pingTimeoutTimer = null;

+    if (typeof addEventListener === "function") {
+      addEventListener("beforeunload", function () {
+        if (_this.transport) {
+          // silently close the transport
+          _this.transport.removeAllListeners();
+
+          _this.transport.close();
+        }
+      }, false);
+    }
+
    _this.open();

    return _this;
@@ -3279,11 +3291,6 @@ var rEscapedNewline = /\\n/g;
 */

 var callbacks;
-/**
- * Noop.
- */
-
-function empty() {}

 var JSONPPolling = /*#__PURE__*/function (_Polling) {
  _inherits(JSONPPolling, _Polling);
@@ -3319,14 +3326,7 @@ var JSONPPolling = /*#__PURE__*/function (_Polling) {
      self.onData(msg);
    }); // append to query string

-    _this.query.j = _this.index; // prevent spurious errors from being emitted when the window is unloaded
-
-    if (typeof addEventListener === "function") {
-      addEventListener("beforeunload", function () {
-        if (self.script) self.script.onerror = empty;
-      }, false);
-    }
-
+    _this.query.j = _this.index;
    return _this;
  }
  /**
@@ -3344,6 +3344,9 @@ var JSONPPolling = /*#__PURE__*/function (_Polling) {
     */
    value: function doClose() {
      if (this.script) {
+        // prevent spurious errors from being emitted when the window is unloaded
+        this.script.onerror = function () {};
+
        this.script.parentNode.removeChild(this.script);
        this.script = null;
      }
@@ -4425,6 +4428,7 @@ var WS = /*#__PURE__*/function (_Transport) {
    value: function doClose() {
      if (typeof this.ws !== "undefined") {
        this.ws.close();
+        this.ws = null;
      }
    }
    /**
@@ -5188,224 +5192,6 @@ function queryKey(uri, query) {

 /***/ }),

-/***/ "./node_modules/process/browser.js":
-/*!*****************************************!*\
-  !*** ./node_modules/process/browser.js ***!
-  \*****************************************/
-/*! no static exports found */
-/***/ (function(module, exports) {
-
-// shim for using process in browser
-var process = module.exports = {}; // cached from whatever global is present so that test runners that stub it
-// don't break things.  But we need to wrap it in a try catch in case it is
-// wrapped in strict mode code which doesn't define any globals.  It's inside a
-// function because try/catches deoptimize in certain engines.
-
-var cachedSetTimeout;
-var cachedClearTimeout;
-
-function defaultSetTimout() {
-  throw new Error('setTimeout has not been defined');
-}
-
-function defaultClearTimeout() {
-  throw new Error('clearTimeout has not been defined');
-}
-
-(function () {
-  try {
-    if (typeof setTimeout === 'function') {
-      cachedSetTimeout = setTimeout;
-    } else {
-      cachedSetTimeout = defaultSetTimout;
-    }
-  } catch (e) {
-    cachedSetTimeout = defaultSetTimout;
-  }
-
-  try {
-    if (typeof clearTimeout === 'function') {
-      cachedClearTimeout = clearTimeout;
-    } else {
-      cachedClearTimeout = defaultClearTimeout;
-    }
-  } catch (e) {
-    cachedClearTimeout = defaultClearTimeout;
-  }
-})();
-
-function runTimeout(fun) {
-  if (cachedSetTimeout === setTimeout) {
-    //normal enviroments in sane situations
-    return setTimeout(fun, 0);
-  } // if setTimeout wasn't available but was latter defined
-
-
-  if ((cachedSetTimeout === defaultSetTimout || !cachedSetTimeout) && setTimeout) {
-    cachedSetTimeout = setTimeout;
-    return setTimeout(fun, 0);
-  }
-
-  try {
-    // when when somebody has screwed with setTimeout but no I.E. maddness
-    return cachedSetTimeout(fun, 0);
-  } catch (e) {
-    try {
-      // When we are in I.E. but the script has been evaled so I.E. doesn't trust the global object when called normally
-      return cachedSetTimeout.call(null, fun, 0);
-    } catch (e) {
-      // same as above but when it's a version of I.E. that must have the global object for 'this', hopfully our context correct otherwise it will throw a global error
-      return cachedSetTimeout.call(this, fun, 0);
-    }
-  }
-}
-
-function runClearTimeout(marker) {
-  if (cachedClearTimeout === clearTimeout) {
-    //normal enviroments in sane situations
-    return clearTimeout(marker);
-  } // if clearTimeout wasn't available but was latter defined
-
-
-  if ((cachedClearTimeout === defaultClearTimeout || !cachedClearTimeout) && clearTimeout) {
-    cachedClearTimeout = clearTimeout;
-    return clearTimeout(marker);
-  }
-
-  try {
-    // when when somebody has screwed with setTimeout but no I.E. maddness
-    return cachedClearTimeout(marker);
-  } catch (e) {
-    try {
-      // When we are in I.E. but the script has been evaled so I.E. doesn't  trust the global object when called normally
-      return cachedClearTimeout.call(null, marker);
-    } catch (e) {
-      // same as above but when it's a version of I.E. that must have the global object for 'this', hopfully our context correct otherwise it will throw a global error.
-      // Some versions of I.E. have different rules for clearTimeout vs setTimeout
-      return cachedClearTimeout.call(this, marker);
-    }
-  }
-}
-
-var queue = [];
-var draining = false;
-var currentQueue;
-var queueIndex = -1;
-
-function cleanUpNextTick() {
-  if (!draining || !currentQueue) {
-    return;
-  }
-
-  draining = false;
-
-  if (currentQueue.length) {
-    queue = currentQueue.concat(queue);
-  } else {
-    queueIndex = -1;
-  }
-
-  if (queue.length) {
-    drainQueue();
-  }
-}
-
-function drainQueue() {
-  if (draining) {
-    return;
-  }
-
-  var timeout = runTimeout(cleanUpNextTick);
-  draining = true;
-  var len = queue.length;
-
-  while (len) {
-    currentQueue = queue;
-    queue = [];
-
-    while (++queueIndex < len) {
-      if (currentQueue) {
-        currentQueue[queueIndex].run();
-      }
-    }
-
-    queueIndex = -1;
-    len = queue.length;
-  }
-
-  currentQueue = null;
-  draining = false;
-  runClearTimeout(timeout);
-}
-
-process.nextTick = function (fun) {
-  var args = new Array(arguments.length - 1);
-
-  if (arguments.length > 1) {
-    for (var i = 1; i < arguments.length; i++) {
-      args[i - 1] = arguments[i];
-    }
-  }
-
-  queue.push(new Item(fun, args));
-
-  if (queue.length === 1 && !draining) {
-    runTimeout(drainQueue);
-  }
-}; // v8 likes predictible objects
-
-
-function Item(fun, array) {
-  this.fun = fun;
-  this.array = array;
-}
-
-Item.prototype.run = function () {
-  this.fun.apply(null, this.array);
-};
-
-process.title = 'browser';
-process.browser = true;
-process.env = {};
-process.argv = [];
-process.version = ''; // empty string to avoid regexp issues
-
-process.versions = {};
-
-function noop() {}
-
-process.on = noop;
-process.addListener = noop;
-process.once = noop;
-process.off = noop;
-process.removeListener = noop;
-process.removeAllListeners = noop;
-process.emit = noop;
-process.prependListener = noop;
-process.prependOnceListener = noop;
-
-process.listeners = function (name) {
-  return [];
-};
-
-process.binding = function (name) {
-  throw new Error('process.binding is not supported');
-};
-
-process.cwd = function () {
-  return '/';
-};
-
-process.chdir = function (dir) {
-  throw new Error('process.chdir is not supported');
-};
-
-process.umask = function () {
-  return 0;
-};
-
-/***/ }),
-
 /***/ "./node_modules/socket.io-parser/dist/binary.js":
 /*!******************************************************!*\
  !*** ./node_modules/socket.io-parser/dist/binary.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/cluster-haproxy/server/Dockerfile
+++ b/examples/cluster-haproxy/server/Dockerfile
@@ -1,4 +1,4 @@
-FROM mhart/alpine-node:6
+FROM node:14-alpine

 # Create app directory
 RUN mkdir -p /usr/src/app
@@ -6,7 +6,7 @@ WORKDIR /usr/src/app

 # Install app dependencies
 COPY package.json /usr/src/app/
-RUN npm install
+RUN npm install --prod

 # Bundle app source
 COPY . /usr/src/app
--- a/examples/cluster-haproxy/server/package.json
+++ b/examples/cluster-haproxy/server/package.json
@@ -8,8 +8,8 @@
  "license": "BSD",
  "dependencies": {
    "express": "4.13.4",
-    "socket.io": "^1.7.2",
-    "socket.io-redis": "^3.0.0"
+    "socket.io": "^3.1.0",
+    "socket.io-redis": "^6.0.1"
  },
  "scripts": {
    "start": "node index.js"
--- a/examples/cluster-httpd/httpd/httpd.conf
+++ b/examples/cluster-httpd/httpd/httpd.conf
@@ -3,6 +3,8 @@ Listen 80

 ServerName localhost

+LoadModule mpm_event_module             modules/mod_mpm_event.so
+
 LoadModule authn_file_module            modules/mod_authn_file.so
 LoadModule authn_core_module            modules/mod_authn_core.so
 LoadModule authz_host_module            modules/mod_authz_host.so
--- a/examples/cluster-httpd/server/Dockerfile
+++ b/examples/cluster-httpd/server/Dockerfile
@@ -6,7 +6,7 @@ WORKDIR /usr/src/app

 # Install app dependencies
 COPY package.json /usr/src/app/
-RUN npm install
+RUN npm install --prod

 # Bundle app source
 COPY . /usr/src/app
--- a/examples/cluster-httpd/server/package.json
+++ b/examples/cluster-httpd/server/package.json
@@ -8,8 +8,8 @@
  "license": "BSD",
  "dependencies": {
    "express": "4.13.4",
-    "socket.io": "^1.7.2",
-    "socket.io-redis": "^3.0.0"
+    "socket.io": "^3.1.0",
+    "socket.io-redis": "^6.0.1"
  },
  "scripts": {
    "start": "node index.js"
--- a/examples/cluster-nginx/README.md
+++ b/examples/cluster-nginx/README.md
@@ -22,6 +22,16 @@ Each node connects to the redis backend, which will enable to broadcast to every
 $ docker-compose stop server-george
 ```

+A `client` container is included in the `docker-compose.yml` file, in order to test the routing.
+
+You can create additional `client` containers with:
+
+```
+$ docker-compose up -d --scale=client=10 client
+# and then
+$ docker-compose logs client
+```
+
 ## Features

 - Multiple users can join a chat room by each entering a unique username
--- a/examples/cluster-nginx/client/Dockerfile
+++ b/examples/cluster-nginx/client/Dockerfile
@@ -0,0 +1,15 @@
+FROM node:14-alpine
+
+# Create app directory
+RUN mkdir -p /usr/src/app
+WORKDIR /usr/src/app
+
+# Install app dependencies
+COPY package.json /usr/src/app/
+RUN npm install --prod
+
+# Bundle app source
+COPY . /usr/src/app
+
+EXPOSE 3000
+CMD [ "npm", "start" ]
--- a/examples/cluster-nginx/client/index.js
+++ b/examples/cluster-nginx/client/index.js
@@ -0,0 +1,13 @@
+const socket = require('socket.io-client')('ws://nginx');
+
+socket.on('connect', () => {
+  console.log('connected');
+});
+
+socket.on('my-name-is', (serverName) => {
+  console.log(`connected to ${serverName}`);
+});
+
+socket.on('disconnect', (reason) => {
+  console.log(`disconnected due to ${reason}`);
+});
--- a/examples/cluster-nginx/client/package.json
+++ b/examples/cluster-nginx/client/package.json
@@ -0,0 +1,15 @@
+{
+  "name": "socket.io-chat",
+  "version": "0.0.0",
+  "description": "A simple chat client using socket.io",
+  "main": "index.js",
+  "author": "Grant Timmerman",
+  "private": true,
+  "license": "MIT",
+  "dependencies": {
+    "socket.io-client": "^3.1.0"
+  },
+  "scripts": {
+    "start": "node index.js"
+  }
+}
--- a/examples/cluster-nginx/docker-compose.yml
+++ b/examples/cluster-nginx/docker-compose.yml
@@ -45,6 +45,11 @@ server-ringo:
  environment:
    - NAME=Ringo

+client:
+  build: ./client
+  links:
+    - nginx
+
 redis:
  image: redis:alpine
  expose:
--- a/examples/cluster-nginx/nginx/nginx.conf
+++ b/examples/cluster-nginx/nginx/nginx.conf
@@ -24,8 +24,12 @@ http {
  }

  upstream nodes {
-    # enable sticky session
-    ip_hash;
+    # enable sticky session with either "hash" (uses the complete IP address)
+    hash $remote_addr consistent;
+    # or "ip_hash" (uses the first three octets of the client IPv4 address, or the entire IPv6 address)
+    # ip_hash;
+    # or "sticky" (needs commercial subscription)
+    # sticky cookie srv_id expires=1h domain=.example.com path=/;

    server server-john:3000;
    server server-paul:3000;
--- a/examples/cluster-nginx/server/Dockerfile
+++ b/examples/cluster-nginx/server/Dockerfile
@@ -1,4 +1,4 @@
-FROM mhart/alpine-node:6
+FROM node:14-alpine

 # Create app directory
 RUN mkdir -p /usr/src/app
@@ -6,7 +6,7 @@ WORKDIR /usr/src/app

 # Install app dependencies
 COPY package.json /usr/src/app/
-RUN npm install
+RUN npm install --prod

 # Bundle app source
 COPY . /usr/src/app
--- a/examples/cluster-nginx/server/package.json
+++ b/examples/cluster-nginx/server/package.json
@@ -8,8 +8,8 @@
  "license": "MIT",
  "dependencies": {
    "express": "4.13.4",
-    "socket.io": "^1.7.2",
-    "socket.io-redis": "^3.0.0"
+    "socket.io": "^3.1.0",
+    "socket.io-redis": "^6.0.1"
  },
  "scripts": {
    "start": "node index.js"
--- a/examples/cluster-traefik/README.md
+++ b/examples/cluster-traefik/README.md
@@ -0,0 +1,22 @@
+
+# Socket.IO Chat with traefik & [redis](https://redis.io/)
+
+A simple chat demo for Socket.IO
+
+## How to use
+
+Install [Docker Compose](https://docs.docker.com/compose/install/), then:
+
+```
+$ docker-compose up -d
+```
+
+And then point your browser to `http://localhost:3000`.
+
+You can then scale the server to multiple instances:
+
+```
+$ docker-compose up -d --scale=server=7
+```
+
+The session stickiness, which is [required](https://socket.io/docs/v3/using-multiple-nodes/) when using multiple Socket.IO server instances, is achieved with a cookie. More information [here](https://doc.traefik.io/traefik/v2.0/routing/services/#sticky-sessions).
--- a/examples/cluster-traefik/docker-compose.yml
+++ b/examples/cluster-traefik/docker-compose.yml
@@ -0,0 +1,27 @@
+version: "3"
+
+services:
+  traefik:
+    image: traefik:2.4
+    volumes:
+      - ./traefik.yml:/etc/traefik/traefik.yml
+      - /var/run/docker.sock:/var/run/docker.sock
+    links:
+      - server
+    ports:
+     - "3000:80"
+     - "8080:8080"
+
+  server:
+    build: ./server
+    links:
+      - redis
+    labels:
+      - "traefik.http.routers.chat.rule=PathPrefix(`/`)"
+      - traefik.http.services.chat.loadBalancer.sticky.cookie.name=server_id
+      - traefik.http.services.chat.loadBalancer.sticky.cookie.httpOnly=true
+
+  redis:
+    image: redis:6-alpine
+    labels:
+      - traefik.enable=false
--- a/examples/cluster-traefik/server/Dockerfile
+++ b/examples/cluster-traefik/server/Dockerfile
@@ -0,0 +1,15 @@
+FROM node:14-alpine
+
+# Create app directory
+RUN mkdir -p /usr/src/app
+WORKDIR /usr/src/app
+
+# Install app dependencies
+COPY package.json /usr/src/app/
+RUN npm install --prod
+
+# Bundle app source
+COPY . /usr/src/app
+
+EXPOSE 3000
+CMD [ "npm", "start" ]
--- a/examples/cluster-traefik/server/index.js
+++ b/examples/cluster-traefik/server/index.js
@@ -0,0 +1,83 @@
+// Setup basic express server
+var express = require('express');
+var app = express();
+var server = require('http').createServer(app);
+var io = require('socket.io')(server);
+var redis = require('socket.io-redis');
+var port = process.env.PORT || 3000;
+var crypto = require('crypto');
+var serverName = crypto.randomBytes(3).toString('hex');
+
+io.adapter(redis({ host: 'redis', port: 6379 }));
+
+server.listen(port, function () {
+  console.log('Server listening at port %d', port);
+  console.log('Hello, I\'m %s, how can I help?', serverName);
+});
+
+// Routing
+app.use(express.static(__dirname + '/public'));
+
+// Chatroom
+
+var numUsers = 0;
+
+io.on('connection', function (socket) {
+  socket.emit('my-name-is', serverName);
+
+  var addedUser = false;
+
+  // when the client emits 'new message', this listens and executes
+  socket.on('new message', function (data) {
+    // we tell the client to execute 'new message'
+    socket.broadcast.emit('new message', {
+      username: socket.username,
+      message: data
+    });
+  });
+
+  // when the client emits 'add user', this listens and executes
+  socket.on('add user', function (username) {
+    if (addedUser) return;
+
+    // we store the username in the socket session for this client
+    socket.username = username;
+    ++numUsers;
+    addedUser = true;
+    socket.emit('login', {
+      numUsers: numUsers
+    });
+    // echo globally (all clients) that a person has connected
+    socket.broadcast.emit('user joined', {
+      username: socket.username,
+      numUsers: numUsers
+    });
+  });
+
+  // when the client emits 'typing', we broadcast it to others
+  socket.on('typing', function () {
+    socket.broadcast.emit('typing', {
+      username: socket.username
+    });
+  });
+
+  // when the client emits 'stop typing', we broadcast it to others
+  socket.on('stop typing', function () {
+    socket.broadcast.emit('stop typing', {
+      username: socket.username
+    });
+  });
+
+  // when the user disconnects.. perform this
+  socket.on('disconnect', function () {
+    if (addedUser) {
+      --numUsers;
+
+      // echo globally that this client has left
+      socket.broadcast.emit('user left', {
+        username: socket.username,
+        numUsers: numUsers
+      });
+    }
+  });
+});
--- a/examples/cluster-traefik/server/package.json
+++ b/examples/cluster-traefik/server/package.json
@@ -0,0 +1,17 @@
+{
+  "name": "socket.io-chat",
+  "version": "0.0.0",
+  "description": "A simple chat client using socket.io",
+  "main": "index.js",
+  "author": "Grant Timmerman",
+  "private": true,
+  "license": "MIT",
+  "dependencies": {
+    "express": "4.13.4",
+    "socket.io": "^3.1.0",
+    "socket.io-redis": "^6.0.1"
+  },
+  "scripts": {
+    "start": "node index.js"
+  }
+}
--- a/examples/cluster-traefik/server/public/index.html
+++ b/examples/cluster-traefik/server/public/index.html
@@ -0,0 +1,28 @@
+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <title>Socket.IO Chat Example</title>
+  <link rel="stylesheet" href="style.css">
+</head>
+<body>
+  <ul class="pages">
+    <li class="chat page">
+      <div class="chatArea">
+        <ul class="messages"></ul>
+      </div>
+      <input class="inputMessage" placeholder="Type here..."/>
+    </li>
+    <li class="login page">
+      <div class="form">
+        <h3 class="title">What's your nickname?</h3>
+        <input class="usernameInput" type="text" maxlength="14" />
+      </div>
+    </li>
+  </ul>
+
+  <script src="https://code.jquery.com/jquery-1.10.2.min.js"></script>
+  <script src="/socket.io/socket.io.js"></script>
+  <script src="/main.js"></script>
+</body>
+</html>
--- a/examples/cluster-traefik/server/public/main.js
+++ b/examples/cluster-traefik/server/public/main.js
@@ -0,0 +1,286 @@
+$(function() {
+  var FADE_TIME = 150; // ms
+  var TYPING_TIMER_LENGTH = 400; // ms
+  var COLORS = [
+    '#e21400', '#91580f', '#f8a700', '#f78b00',
+    '#58dc00', '#287b00', '#a8f07a', '#4ae8c4',
+    '#3b88eb', '#3824aa', '#a700ff', '#d300e7'
+  ];
+
+  // Initialize variables
+  var $window = $(window);
+  var $usernameInput = $('.usernameInput'); // Input for username
+  var $messages = $('.messages'); // Messages area
+  var $inputMessage = $('.inputMessage'); // Input message input box
+
+  var $loginPage = $('.login.page'); // The login page
+  var $chatPage = $('.chat.page'); // The chatroom page
+
+  // Prompt for setting a username
+  var username;
+  var connected = false;
+  var typing = false;
+  var lastTypingTime;
+  var $currentInput = $usernameInput.focus();
+
+  var socket = io();
+
+  function addParticipantsMessage (data) {
+    var message = '';
+    if (data.numUsers === 1) {
+      message += "there's 1 participant";
+    } else {
+      message += "there are " + data.numUsers + " participants";
+    }
+    log(message);
+  }
+
+  // Sets the client's username
+  function setUsername () {
+    username = cleanInput($usernameInput.val().trim());
+
+    // If the username is valid
+    if (username) {
+      $loginPage.fadeOut();
+      $chatPage.show();
+      $loginPage.off('click');
+      $currentInput = $inputMessage.focus();
+
+      // Tell the server your username
+      socket.emit('add user', username);
+    }
+  }
+
+  // Sends a chat message
+  function sendMessage () {
+    var message = $inputMessage.val();
+    // Prevent markup from being injected into the message
+    message = cleanInput(message);
+    // if there is a non-empty message and a socket connection
+    if (message && connected) {
+      $inputMessage.val('');
+      addChatMessage({
+        username: username,
+        message: message
+      });
+      // tell server to execute 'new message' and send along one parameter
+      socket.emit('new message', message);
+    }
+  }
+
+  // Log a message
+  function log (message, options) {
+    var $el = $('<li>').addClass('log').text(message);
+    addMessageElement($el, options);
+  }
+
+  // Adds the visual chat message to the message list
+  function addChatMessage (data, options) {
+    // Don't fade the message in if there is an 'X was typing'
+    var $typingMessages = getTypingMessages(data);
+    options = options || {};
+    if ($typingMessages.length !== 0) {
+      options.fade = false;
+      $typingMessages.remove();
+    }
+
+    var $usernameDiv = $('<span class="username"/>')
+      .text(data.username)
+      .css('color', getUsernameColor(data.username));
+    var $messageBodyDiv = $('<span class="messageBody">')
+      .text(data.message);
+
+    var typingClass = data.typing ? 'typing' : '';
+    var $messageDiv = $('<li class="message"/>')
+      .data('username', data.username)
+      .addClass(typingClass)
+      .append($usernameDiv, $messageBodyDiv);
+
+    addMessageElement($messageDiv, options);
+  }
+
+  // Adds the visual chat typing message
+  function addChatTyping (data) {
+    data.typing = true;
+    data.message = 'is typing';
+    addChatMessage(data);
+  }
+
+  // Removes the visual chat typing message
+  function removeChatTyping (data) {
+    getTypingMessages(data).fadeOut(function () {
+      $(this).remove();
+    });
+  }
+
+  // Adds a message element to the messages and scrolls to the bottom
+  // el - The element to add as a message
+  // options.fade - If the element should fade-in (default = true)
+  // options.prepend - If the element should prepend
+  //   all other messages (default = false)
+  function addMessageElement (el, options) {
+    var $el = $(el);
+
+    // Setup default options
+    if (!options) {
+      options = {};
+    }
+    if (typeof options.fade === 'undefined') {
+      options.fade = true;
+    }
+    if (typeof options.prepend === 'undefined') {
+      options.prepend = false;
+    }
+
+    // Apply options
+    if (options.fade) {
+      $el.hide().fadeIn(FADE_TIME);
+    }
+    if (options.prepend) {
+      $messages.prepend($el);
+    } else {
+      $messages.append($el);
+    }
+    $messages[0].scrollTop = $messages[0].scrollHeight;
+  }
+
+  // Prevents input from having injected markup
+  function cleanInput (input) {
+    return $('<div/>').text(input).text();
+  }
+
+  // Updates the typing event
+  function updateTyping () {
+    if (connected) {
+      if (!typing) {
+        typing = true;
+        socket.emit('typing');
+      }
+      lastTypingTime = (new Date()).getTime();
+
+      setTimeout(function () {
+        var typingTimer = (new Date()).getTime();
+        var timeDiff = typingTimer - lastTypingTime;
+        if (timeDiff >= TYPING_TIMER_LENGTH && typing) {
+          socket.emit('stop typing');
+          typing = false;
+        }
+      }, TYPING_TIMER_LENGTH);
+    }
+  }
+
+  // Gets the 'X is typing' messages of a user
+  function getTypingMessages (data) {
+    return $('.typing.message').filter(function (i) {
+      return $(this).data('username') === data.username;
+    });
+  }
+
+  // Gets the color of a username through our hash function
+  function getUsernameColor (username) {
+    // Compute hash code
+    var hash = 7;
+    for (var i = 0; i < username.length; i++) {
+       hash = username.charCodeAt(i) + (hash << 5) - hash;
+    }
+    // Calculate color
+    var index = Math.abs(hash % COLORS.length);
+    return COLORS[index];
+  }
+
+  // Keyboard events
+
+  $window.keydown(function (event) {
+    // Auto-focus the current input when a key is typed
+    if (!(event.ctrlKey || event.metaKey || event.altKey)) {
+      $currentInput.focus();
+    }
+    // When the client hits ENTER on their keyboard
+    if (event.which === 13) {
+      if (username) {
+        sendMessage();
+        socket.emit('stop typing');
+        typing = false;
+      } else {
+        setUsername();
+      }
+    }
+  });
+
+  $inputMessage.on('input', function() {
+    updateTyping();
+  });
+
+  // Click events
+
+  // Focus input when clicking anywhere on login page
+  $loginPage.click(function () {
+    $currentInput.focus();
+  });
+
+  // Focus input when clicking on the message input's border
+  $inputMessage.click(function () {
+    $inputMessage.focus();
+  });
+
+  // Socket events
+
+  // Whenever the server emits 'login', log the login message
+  socket.on('login', function (data) {
+    connected = true;
+    // Display the welcome message
+    var message = "Welcome to Socket.IO Chat – ";
+    log(message, {
+      prepend: true
+    });
+    addParticipantsMessage(data);
+  });
+
+  // Whenever the server emits 'new message', update the chat body
+  socket.on('new message', function (data) {
+    addChatMessage(data);
+  });
+
+  // Whenever the server emits 'user joined', log it in the chat body
+  socket.on('user joined', function (data) {
+    log(data.username + ' joined');
+    addParticipantsMessage(data);
+  });
+
+  // Whenever the server emits 'user left', log it in the chat body
+  socket.on('user left', function (data) {
+    log(data.username + ' left');
+    addParticipantsMessage(data);
+    removeChatTyping(data);
+  });
+
+  // Whenever the server emits 'typing', show the typing message
+  socket.on('typing', function (data) {
+    addChatTyping(data);
+  });
+
+  // Whenever the server emits 'stop typing', kill the typing message
+  socket.on('stop typing', function (data) {
+    removeChatTyping(data);
+  });
+
+  socket.on('disconnect', function () {
+    log('you have been disconnected');
+  });
+
+  socket.on('connect', function () {
+    if (username) {
+      log('you have been reconnected');
+      socket.emit('add user', username);
+    }
+  });
+
+  socket.io.on('reconnect_error', function () {
+    log('attempt to reconnect has failed');
+  });
+
+  socket.on('my-name-is', function (serverName) {
+    log('host is now ' + serverName);
+  })
+
+});
--- a/examples/cluster-traefik/server/public/style.css
+++ b/examples/cluster-traefik/server/public/style.css
@@ -0,0 +1,149 @@
+/* Fix user-agent */
+
+* {
+  box-sizing: border-box;
+}
+
+html {
+  font-weight: 300;
+  -webkit-font-smoothing: antialiased;
+}
+
+html, input {
+  font-family:
+    "HelveticaNeue-Light",
+    "Helvetica Neue Light",
+    "Helvetica Neue",
+    Helvetica,
+    Arial,
+    "Lucida Grande",
+    sans-serif;
+}
+
+html, body {
+  height: 100%;
+  margin: 0;
+  padding: 0;
+}
+
+ul {
+  list-style: none;
+  word-wrap: break-word;
+}
+
+/* Pages */
+
+.pages {
+  height: 100%;
+  margin: 0;
+  padding: 0;
+  width: 100%;
+}
+
+.page {
+  height: 100%;
+  position: absolute;
+  width: 100%;
+}
+
+/* Login Page */
+
+.login.page {
+  background-color: #000;
+}
+
+.login.page .form {
+  height: 100px;
+  margin-top: -100px;
+  position: absolute;
+
+  text-align: center;
+  top: 50%;
+  width: 100%;
+}
+
+.login.page .form .usernameInput {
+  background-color: transparent;
+  border: none;
+  border-bottom: 2px solid #fff;
+  outline: none;
+  padding-bottom: 15px;
+  text-align: center;
+  width: 400px;
+}
+
+.login.page .title {
+  font-size: 200%;
+}
+
+.login.page .usernameInput {
+  font-size: 200%;
+  letter-spacing: 3px;
+}
+
+.login.page .title, .login.page .usernameInput {
+  color: #fff;
+  font-weight: 100;
+}
+
+/* Chat page */
+
+.chat.page {
+  display: none;
+}
+
+/* Font */
+
+.messages {
+  font-size: 150%;
+}
+
+.inputMessage {
+  font-size: 100%;
+}
+
+.log {
+  color: gray;
+  font-size: 70%;
+  margin: 5px;
+  text-align: center;
+}
+
+/* Messages */
+
+.chatArea {
+  height: 100%;
+  padding-bottom: 60px;
+}
+
+.messages {
+  height: 100%;
+  margin: 0;
+  overflow-y: scroll;
+  padding: 10px 20px 10px 20px;
+}
+
+.message.typing .messageBody {
+  color: gray;
+}
+
+.username {
+  font-weight: 700;
+  overflow: hidden;
+  padding-right: 15px;
+  text-align: right;
+}
+
+/* Input */
+
+.inputMessage {
+  border: 10px solid #000;
+  bottom: 0;
+  height: 60px;
+  left: 0;
+  outline: none;
+  padding-left: 10px;
+  position: absolute;
+  right: 0;
+  width: 100%;
+}
--- a/examples/cluster-traefik/traefik.yml
+++ b/examples/cluster-traefik/traefik.yml
@@ -0,0 +1,10 @@
+
+api:
+  insecure: true
+
+entryPoints:
+  web:
+    address: ":80"
+
+providers:
+  docker: {}
--- a/examples/private-messaging/.gitignore
+++ b/examples/private-messaging/.gitignore
@@ -0,0 +1,24 @@
+.DS_Store
+node_modules
+/dist
+
+
+# local env files
+.env.local
+.env.*.local
+
+# Log files
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+
+# Editor directories and files
+.idea
+.vscode
+*.suo
+*.ntvs*
+*.njsproj
+*.sln
+*.sw?
+package-lock.json
--- a/examples/private-messaging/README.md
+++ b/examples/private-messaging/README.md
@@ -0,0 +1,23 @@
+# Private messaging with Socket.IO
+
+Please read the related guide:
+
+- [Part I](https://socket.io/get-started/private-messaging-part-1/): initial implementation
+- [Part II](https://socket.io/get-started/private-messaging-part-2/): persistent user ID
+- [Part III](https://socket.io/get-started/private-messaging-part-3/): persistent messages
+- [Part IV](https://socket.io/get-started/private-messaging-part-4/): scaling up
+
+## Running the frontend
+
+```
+npm install
+npm run serve
+```
+
+### Running the server
+
+```
+cd server
+npm install
+npm start
+```
--- a/examples/private-messaging/babel.config.js
+++ b/examples/private-messaging/babel.config.js
@@ -0,0 +1,5 @@
+module.exports = {
+  presets: [
+    '@vue/cli-plugin-babel/preset'
+  ]
+}
--- a/examples/private-messaging/package.json
+++ b/examples/private-messaging/package.json
@@ -0,0 +1,43 @@
+{
+  "name": "private-messaging",
+  "version": "0.1.0",
+  "private": true,
+  "scripts": {
+    "serve": "vue-cli-service serve",
+    "build": "vue-cli-service build",
+    "lint": "vue-cli-service lint"
+  },
+  "dependencies": {
+    "core-js": "^3.6.5",
+    "socket.io-client": "^3.1.1",
+    "vue": "^2.6.11"
+  },
+  "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"
+  },
+  "eslintConfig": {
+    "root": true,
+    "env": {
+      "node": true
+    },
+    "extends": [
+      "plugin:vue/essential",
+      "eslint:recommended"
+    ],
+    "parserOptions": {
+      "parser": "babel-eslint"
+    },
+    "rules": {}
+  },
+  "browserslist": [
+    "> 1%",
+    "last 2 versions",
+    "not dead"
+  ]
+}
--- a/examples/private-messaging/public/favicon.ico
+++ b/examples/private-messaging/public/favicon.ico
--- a/examples/private-messaging/public/fonts/Lato-Regular.ttf
+++ b/examples/private-messaging/public/fonts/Lato-Regular.ttf
--- a/examples/private-messaging/public/index.html
+++ b/examples/private-messaging/public/index.html
@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html lang="">
+  <head>
+    <meta charset="utf-8">
+    <meta http-equiv="X-UA-Compatible" content="IE=edge">
+    <meta name="viewport" content="width=device-width,initial-scale=1.0">
+    <link rel="icon" href="<%= BASE_URL %>favicon.ico">
+    <title>Private messaging with Socket.IO</title>
+  </head>
+  <body>
+    <noscript>
+      <strong>We're sorry but this application doesn't work properly without JavaScript enabled. Please enable it to continue.</strong>
+    </noscript>
+    <div id="app"></div>
+    <!-- built files will be auto injected -->
+  </body>
+</html>
--- a/examples/private-messaging/server/cluster.js
+++ b/examples/private-messaging/server/cluster.js
@@ -0,0 +1,31 @@
+const cluster = require("cluster");
+const http = require("http");
+const { setupMaster } = require("@socket.io/sticky");
+
+const WORKERS_COUNT = 4;
+
+if (cluster.isMaster) {
+  console.log(`Master ${process.pid} is running`);
+
+  for (let i = 0; i < WORKERS_COUNT; i++) {
+    cluster.fork();
+  }
+
+  cluster.on("exit", (worker) => {
+    console.log(`Worker ${worker.process.pid} died`);
+    cluster.fork();
+  });
+
+  const httpServer = http.createServer();
+  setupMaster(httpServer, {
+    loadBalancingMethod: "least-connection", // either "random", "round-robin" or "least-connection"
+  });
+  const PORT = process.env.PORT || 3000;
+
+  httpServer.listen(PORT, () =>
+    console.log(`server listening at http://localhost:${PORT}`)
+  );
+} else {
+  console.log(`Worker ${process.pid} started`);
+  require("./index");
+}
--- a/examples/private-messaging/server/docker-compose.yml
+++ b/examples/private-messaging/server/docker-compose.yml
@@ -0,0 +1,7 @@
+version: "3"
+
+services:
+  redis:
+    image: redis:5
+    ports:
+      - "6379:6379"
--- a/examples/private-messaging/server/index.js
+++ b/examples/private-messaging/server/index.js
@@ -0,0 +1,125 @@
+const httpServer = require("http").createServer();
+const Redis = require("ioredis");
+const redisClient = new Redis();
+const io = require("socket.io")(httpServer, {
+  cors: {
+    origin: "http://localhost:8080",
+  },
+  adapter: require("socket.io-redis")({
+    pubClient: redisClient,
+    subClient: redisClient.duplicate(),
+  }),
+});
+
+const { setupWorker } = require("@socket.io/sticky");
+const crypto = require("crypto");
+const randomId = () => crypto.randomBytes(8).toString("hex");
+
+const { RedisSessionStore } = require("./sessionStore");
+const sessionStore = new RedisSessionStore(redisClient);
+
+const { RedisMessageStore } = require("./messageStore");
+const messageStore = new RedisMessageStore(redisClient);
+
+io.use(async (socket, next) => {
+  const sessionID = socket.handshake.auth.sessionID;
+  if (sessionID) {
+    const session = await sessionStore.findSession(sessionID);
+    if (session) {
+      socket.sessionID = sessionID;
+      socket.userID = session.userID;
+      socket.username = session.username;
+      return next();
+    }
+  }
+  const username = socket.handshake.auth.username;
+  if (!username) {
+    return next(new Error("invalid username"));
+  }
+  socket.sessionID = randomId();
+  socket.userID = randomId();
+  socket.username = username;
+  next();
+});
+
+io.on("connection", async (socket) => {
+  // persist session
+  sessionStore.saveSession(socket.sessionID, {
+    userID: socket.userID,
+    username: socket.username,
+    connected: true,
+  });
+
+  // emit session details
+  socket.emit("session", {
+    sessionID: socket.sessionID,
+    userID: socket.userID,
+  });
+
+  // join the "userID" room
+  socket.join(socket.userID);
+
+  // fetch existing users
+  const users = [];
+  const [messages, sessions] = await Promise.all([
+    messageStore.findMessagesForUser(socket.userID),
+    sessionStore.findAllSessions(),
+  ]);
+  const messagesPerUser = new Map();
+  messages.forEach((message) => {
+    const { from, to } = message;
+    const otherUser = socket.userID === from ? to : from;
+    if (messagesPerUser.has(otherUser)) {
+      messagesPerUser.get(otherUser).push(message);
+    } else {
+      messagesPerUser.set(otherUser, [message]);
+    }
+  });
+
+  sessions.forEach((session) => {
+    users.push({
+      userID: session.userID,
+      username: session.username,
+      connected: session.connected,
+      messages: messagesPerUser.get(session.userID) || [],
+    });
+  });
+  socket.emit("users", users);
+
+  // notify existing users
+  socket.broadcast.emit("user connected", {
+    userID: socket.userID,
+    username: socket.username,
+    connected: true,
+    messages: [],
+  });
+
+  // forward the private message to the right recipient (and to other tabs of the sender)
+  socket.on("private message", ({ content, to }) => {
+    const message = {
+      content,
+      from: socket.userID,
+      to,
+    };
+    socket.to(to).to(socket.userID).emit("private message", message);
+    messageStore.saveMessage(message);
+  });
+
+  // notify users upon disconnection
+  socket.on("disconnect", async () => {
+    const matchingSockets = await io.in(socket.userID).allSockets();
+    const isDisconnected = matchingSockets.size === 0;
+    if (isDisconnected) {
+      // notify other users
+      socket.broadcast.emit("user disconnected", socket.userID);
+      // update the connection status of the session
+      sessionStore.saveSession(socket.sessionID, {
+        userID: socket.userID,
+        username: socket.username,
+        connected: false,
+      });
+    }
+  });
+});
+
+setupWorker(io);
--- a/examples/private-messaging/server/messageStore.js
+++ b/examples/private-messaging/server/messageStore.js
@@ -0,0 +1,54 @@
+/* abstract */ class MessageStore {
+  saveMessage(message) {}
+  findMessagesForUser(userID) {}
+}
+
+class InMemoryMessageStore extends MessageStore {
+  constructor() {
+    super();
+    this.messages = [];
+  }
+
+  saveMessage(message) {
+    this.messages.push(message);
+  }
+
+  findMessagesForUser(userID) {
+    return this.messages.filter(
+      ({ from, to }) => from === userID || to === userID
+    );
+  }
+}
+
+const CONVERSATION_TTL = 24 * 60 * 60;
+
+class RedisMessageStore extends MessageStore {
+  constructor(redisClient) {
+    super();
+    this.redisClient = redisClient;
+  }
+
+  saveMessage(message) {
+    const value = JSON.stringify(message);
+    this.redisClient
+      .multi()
+      .rpush(`messages:${message.from}`, value)
+      .rpush(`messages:${message.to}`, value)
+      .expire(`messages:${message.from}`, CONVERSATION_TTL)
+      .expire(`messages:${message.to}`, CONVERSATION_TTL)
+      .exec();
+  }
+
+  findMessagesForUser(userID) {
+    return this.redisClient
+      .lrange(`messages:${userID}`, 0, -1)
+      .then((results) => {
+        return results.map((result) => JSON.parse(result));
+      });
+  }
+}
+
+module.exports = {
+  InMemoryMessageStore,
+  RedisMessageStore,
+};
--- a/examples/private-messaging/server/package.json
+++ b/examples/private-messaging/server/package.json
@@ -0,0 +1,17 @@
+{
+  "name": "server",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "start": "node cluster.js"
+  },
+  "author": "Damien Arrachequesne <damien.arrachequesne@gmail.com>",
+  "license": "MIT",
+  "dependencies": {
+    "@socket.io/sticky": "^1.0.0",
+    "ioredis": "^4.22.0",
+    "socket.io": "^3.1.1",
+    "socket.io-redis": "^6.0.1"
+  }
+}
--- a/examples/private-messaging/server/sessionStore.js
+++ b/examples/private-messaging/server/sessionStore.js
@@ -0,0 +1,89 @@
+/* abstract */ class SessionStore {
+  findSession(id) {}
+  saveSession(id, session) {}
+  findAllSessions() {}
+}
+
+class InMemorySessionStore extends SessionStore {
+  constructor() {
+    super();
+    this.sessions = new Map();
+  }
+
+  findSession(id) {
+    return this.sessions.get(id);
+  }
+
+  saveSession(id, session) {
+    this.sessions.set(id, session);
+  }
+
+  findAllSessions() {
+    return [...this.sessions.values()];
+  }
+}
+
+const SESSION_TTL = 24 * 60 * 60;
+const mapSession = ([userID, username, connected]) =>
+  userID ? { userID, username, connected: connected === "true" } : undefined;
+
+class RedisSessionStore extends SessionStore {
+  constructor(redisClient) {
+    super();
+    this.redisClient = redisClient;
+  }
+
+  findSession(id) {
+    return this.redisClient
+      .hmget(`session:${id}`, "userID", "username", "connected")
+      .then(mapSession);
+  }
+
+  saveSession(id, { userID, username, connected }) {
+    this.redisClient
+      .multi()
+      .hset(
+        `session:${id}`,
+        "userID",
+        userID,
+        "username",
+        username,
+        "connected",
+        connected
+      )
+      .expire(`session:${id}`, SESSION_TTL)
+      .exec();
+  }
+
+  async findAllSessions() {
+    const keys = new Set();
+    let nextIndex = 0;
+    do {
+      const [nextIndexAsStr, results] = await this.redisClient.scan(
+        nextIndex,
+        "MATCH",
+        "session:*",
+        "COUNT",
+        "100"
+      );
+      nextIndex = parseInt(nextIndexAsStr, 10);
+      results.forEach((s) => keys.add(s));
+    } while (nextIndex !== 0);
+    const commands = [];
+    keys.forEach((key) => {
+      commands.push(["hmget", key, "userID", "username", "connected"]);
+    });
+    return this.redisClient
+      .multi(commands)
+      .exec()
+      .then((results) => {
+        return results
+          .map(([err, session]) => (err ? undefined : mapSession(session)))
+          .filter((v) => !!v);
+      });
+  }
+}
+module.exports = {
+  InMemorySessionStore,
+  RedisSessionStore,
+};
--- a/examples/private-messaging/src/App.vue
+++ b/examples/private-messaging/src/App.vue
@@ -0,0 +1,78 @@
+<template>
+  <div id="app">
+    <select-username
+      v-if="!usernameAlreadySelected"
+      @input="onUsernameSelection"
+    />
+    <chat v-else />
+  </div>
+</template>
+
+<script>
+import SelectUsername from "./components/SelectUsername";
+import Chat from "./components/Chat";
+import socket from "./socket";
+
+export default {
+  name: "App",
+  components: {
+    Chat,
+    SelectUsername,
+  },
+  data() {
+    return {
+      usernameAlreadySelected: false,
+    };
+  },
+  methods: {
+    onUsernameSelection(username) {
+      this.usernameAlreadySelected = true;
+      socket.auth = { username };
+      socket.connect();
+    },
+  },
+  created() {
+    const sessionID = localStorage.getItem("sessionID");
+
+    if (sessionID) {
+      this.usernameAlreadySelected = true;
+      socket.auth = { sessionID };
+      socket.connect();
+    }
+
+    socket.on("session", ({ sessionID, userID }) => {
+      // attach the session ID to the next reconnection attempts
+      socket.auth = { sessionID };
+      // store it in the localStorage
+      localStorage.setItem("sessionID", sessionID);
+      // save the ID of the user
+      socket.userID = userID;
+    });
+
+    socket.on("connect_error", (err) => {
+      if (err.message === "invalid username") {
+        this.usernameAlreadySelected = false;
+      }
+    });
+  },
+  destroyed() {
+    socket.off("connect_error");
+  },
+};
+</script>
+
+<style>
+body {
+  margin: 0;
+}
+
+@font-face {
+  font-family: Lato;
+  src: url("/fonts/Lato-Regular.ttf");
+}
+
+#app {
+  font-family: Lato, Arial, sans-serif;
+  font-size: 14px;
+}
+</style>
--- a/examples/private-messaging/src/components/Chat.vue
+++ b/examples/private-messaging/src/components/Chat.vue
@@ -0,0 +1,165 @@
+<template>
+  <div>
+    <div class="left-panel">
+      <user
+        v-for="user in users"
+        :key="user.userID"
+        :user="user"
+        :selected="selectedUser === user"
+        @select="onSelectUser(user)"
+      />
+    </div>
+    <message-panel
+      v-if="selectedUser"
+      :user="selectedUser"
+      @input="onMessage"
+      class="right-panel"
+    />
+  </div>
+</template>
+
+<script>
+import socket from "../socket";
+import User from "./User";
+import MessagePanel from "./MessagePanel";
+
+export default {
+  name: "Chat",
+  components: { User, MessagePanel },
+  data() {
+    return {
+      selectedUser: null,
+      users: [],
+    };
+  },
+  methods: {
+    onMessage(content) {
+      if (this.selectedUser) {
+        socket.emit("private message", {
+          content,
+          to: this.selectedUser.userID,
+        });
+        this.selectedUser.messages.push({
+          content,
+          fromSelf: true,
+        });
+      }
+    },
+    onSelectUser(user) {
+      this.selectedUser = user;
+      user.hasNewMessages = false;
+    },
+  },
+  created() {
+    socket.on("connect", () => {
+      this.users.forEach((user) => {
+        if (user.self) {
+          user.connected = true;
+        }
+      });
+    });
+
+    socket.on("disconnect", () => {
+      this.users.forEach((user) => {
+        if (user.self) {
+          user.connected = false;
+        }
+      });
+    });
+
+    const initReactiveProperties = (user) => {
+      user.hasNewMessages = false;
+    };
+
+    socket.on("users", (users) => {
+      users.forEach((user) => {
+        user.messages.forEach((message) => {
+          message.fromSelf = message.from === socket.userID;
+        });
+        for (let i = 0; i < this.users.length; i++) {
+          const existingUser = this.users[i];
+          if (existingUser.userID === user.userID) {
+            existingUser.connected = user.connected;
+            existingUser.messages = user.messages;
+            return;
+          }
+        }
+        user.self = user.userID === socket.userID;
+        initReactiveProperties(user);
+        this.users.push(user);
+      });
+      // put the current user first, and sort by username
+      this.users.sort((a, b) => {
+        if (a.self) return -1;
+        if (b.self) return 1;
+        if (a.username < b.username) return -1;
+        return a.username > b.username ? 1 : 0;
+      });
+    });
+
+    socket.on("user connected", (user) => {
+      for (let i = 0; i < this.users.length; i++) {
+        const existingUser = this.users[i];
+        if (existingUser.userID === user.userID) {
+          existingUser.connected = true;
+          return;
+        }
+      }
+      initReactiveProperties(user);
+      this.users.push(user);
+    });
+
+    socket.on("user disconnected", (id) => {
+      for (let i = 0; i < this.users.length; i++) {
+        const user = this.users[i];
+        if (user.userID === id) {
+          user.connected = false;
+          break;
+        }
+      }
+    });
+
+    socket.on("private message", ({ content, from, to }) => {
+      for (let i = 0; i < this.users.length; i++) {
+        const user = this.users[i];
+        const fromSelf = socket.userID === from;
+        if (user.userID === (fromSelf ? to : from)) {
+          user.messages.push({
+            content,
+            fromSelf,
+          });
+          if (user !== this.selectedUser) {
+            user.hasNewMessages = true;
+          }
+          break;
+        }
+      }
+    });
+  },
+  destroyed() {
+    socket.off("connect");
+    socket.off("disconnect");
+    socket.off("users");
+    socket.off("user connected");
+    socket.off("user disconnected");
+    socket.off("private message");
+  },
+};
+</script>
+
+<style scoped>
+.left-panel {
+  position: fixed;
+  left: 0;
+  top: 0;
+  bottom: 0;
+  width: 260px;
+  overflow-x: hidden;
+  background-color: #3f0e40;
+  color: white;
+}
+
+.right-panel {
+  margin-left: 260px;
+}
+</style>
--- a/examples/private-messaging/src/components/MessagePanel.vue
+++ b/examples/private-messaging/src/components/MessagePanel.vue
@@ -0,0 +1,101 @@
+<template>
+  <div>
+    <div class="header">
+      <status-icon :connected="user.connected" />{{ user.username }}
+    </div>
+
+    <ul class="messages">
+      <li
+        v-for="(message, index) in user.messages"
+        :key="index"
+        class="message"
+      >
+        <div v-if="displaySender(message, index)" class="sender">
+          {{ message.fromSelf ? "(yourself)" : user.username }}
+        </div>
+        {{ message.content }}
+      </li>
+    </ul>
+
+    <form @submit.prevent="onSubmit" class="form">
+      <textarea v-model="input" placeholder="Your message..." class="input" />
+      <button :disabled="!isValid" class="send-button">Send</button>
+    </form>
+  </div>
+</template>
+
+<script>
+import StatusIcon from "./StatusIcon";
+
+export default {
+  name: "MessagePanel",
+  components: {
+    StatusIcon,
+  },
+  props: {
+    user: Object,
+  },
+  data() {
+    return {
+      input: "",
+    };
+  },
+  methods: {
+    onSubmit() {
+      this.$emit("input", this.input);
+      this.input = "";
+    },
+    displaySender(message, index) {
+      return (
+        index === 0 ||
+        this.user.messages[index - 1].fromSelf !==
+          this.user.messages[index].fromSelf
+      );
+    },
+  },
+  computed: {
+    isValid() {
+      return this.input.length > 0;
+    },
+  },
+};
+</script>
+
+<style scoped>
+.header {
+  line-height: 40px;
+  padding: 10px 20px;
+  border-bottom: 1px solid #dddddd;
+}
+
+.messages {
+  margin: 0;
+  padding: 20px;
+}
+
+.message {
+  list-style: none;
+}
+
+.sender {
+  font-weight: bold;
+  margin-top: 5px;
+}
+
+.form {
+  padding: 10px;
+}
+
+.input {
+  width: 80%;
+  resize: none;
+  padding: 10px;
+  line-height: 1.5;
+  border-radius: 5px;
+  border: 1px solid #000;
+}
+
+.send-button {
+  vertical-align: top;
+}
+</style>
--- a/examples/private-messaging/src/components/SelectUsername.vue
+++ b/examples/private-messaging/src/components/SelectUsername.vue
@@ -0,0 +1,36 @@
+<template>
+  <div class="select-username">
+    <form @submit.prevent="onSubmit">
+      <input v-model="username" placeholder="Your username..." />
+      <button :disabled="!isValid">Send</button>
+    </form>
+  </div>
+</template>
+
+<script>
+export default {
+  name: "SelectUsername",
+  data() {
+    return {
+      username: "",
+    };
+  },
+  computed: {
+    isValid() {
+      return this.username.length > 2;
+    },
+  },
+  methods: {
+    onSubmit() {
+      this.$emit("input", this.username);
+    },
+  },
+};
+</script>
+
+<style scoped>
+.select-username {
+  width: 300px;
+  margin: 200px auto 0;
+}
+</style>
--- a/examples/private-messaging/src/components/StatusIcon.vue
+++ b/examples/private-messaging/src/components/StatusIcon.vue
@@ -0,0 +1,27 @@
+<template>
+  <i class="icon" :class="{ connected: connected }"></i>
+</template>
+
+<script>
+export default {
+  name: "StatusIcon",
+  props: {
+    connected: Boolean,
+  },
+};
+</script>
+
+<style scoped>
+.icon {
+  height: 8px;
+  width: 8px;
+  border-radius: 50%;
+  display: inline-block;
+  background-color: #e38968;
+  margin-right: 6px;
+}
+
+.icon.connected {
+  background-color: #86bb71;
+}
+</style>
--- a/examples/private-messaging/src/components/User.vue
+++ b/examples/private-messaging/src/components/User.vue
@@ -0,0 +1,63 @@
+<template>
+  <div class="user" @click="onClick" :class="{ selected: selected }">
+    <div class="description">
+      <div class="name">
+        {{ user.username }} {{ user.self ? " (yourself)" : "" }}
+      </div>
+      <div class="status">
+        <status-icon :connected="user.connected" />{{ status }}
+      </div>
+    </div>
+    <div v-if="user.hasNewMessages" class="new-messages">!</div>
+  </div>
+</template>
+
+<script>
+import StatusIcon from "./StatusIcon";
+export default {
+  name: "User",
+  components: { StatusIcon },
+  props: {
+    user: Object,
+    selected: Boolean,
+  },
+  methods: {
+    onClick() {
+      this.$emit("select");
+    },
+  },
+  computed: {
+    status() {
+      return this.user.connected ? "online" : "offline";
+    },
+  },
+};
+</script>
+
+<style scoped>
+.selected {
+  background-color: #1164a3;
+}
+
+.user {
+  padding: 10px;
+}
+
+.description {
+  display: inline-block;
+}
+
+.status {
+  color: #92959e;
+}
+
+.new-messages {
+  color: white;
+  background-color: red;
+  width: 20px;
+  border-radius: 5px;
+  text-align: center;
+  float: right;
+  margin-top: 10px;
+}
+</style>
--- a/examples/private-messaging/src/main.js
+++ b/examples/private-messaging/src/main.js
@@ -0,0 +1,8 @@
+import Vue from "vue";
+import App from "./App.vue";
+
+Vue.config.productionTip = false;
+
+new Vue({
+  render: (h) => h(App),
+}).$mount("#app");
--- a/examples/private-messaging/src/socket.js
+++ b/examples/private-messaging/src/socket.js
@@ -0,0 +1,10 @@
+import { io } from "socket.io-client";
+
+const URL = "http://localhost:3000";
+const socket = io(URL, { autoConnect: false });
+
+socket.onAny((event, ...args) => {
+  console.log(event, args);
+});
+
+export default socket;
--- a/lib/client.ts
+++ b/lib/client.ts
@@ -1,5 +1,6 @@
 import { Decoder, Encoder, Packet, PacketType } from "socket.io-parser";
 import debugModule = require("debug");
+import url = require("url");
 import type { IncomingMessage } from "http";
 import type { Namespace, Server } from "./index";
 import type { Socket } from "./socket";
@@ -77,7 +78,7 @@ export class Client {
   * @param {Object} auth - the auth parameters
   * @private
   */
-  private connect(name: string, auth: object = {}) {
+  private connect(name: string, auth: object = {}): void {
    if (this.server._nsps.has(name)) {
      debug("connecting to namespace %s", name);
      return this.doConnect(name, auth);
@@ -112,7 +113,7 @@ export class Client {
   *
   * @private
   */
-  private doConnect(name: string, auth: object) {
+  private doConnect(name: string, auth: object): void {
    const nsp = this.server.of(name);

    const socket = nsp._add(this, auth, () => {
@@ -131,7 +132,7 @@ export class Client {
   *
   * @private
   */
-  _disconnect() {
+  _disconnect(): void {
    for (const socket of this.sockets.values()) {
      socket.disconnect();
    }
@@ -144,7 +145,7 @@ export class Client {
   *
   * @private
   */
-  _remove(socket: Socket) {
+  _remove(socket: Socket): void {
    if (this.sockets.has(socket.id)) {
      const nsp = this.sockets.get(socket.id)!.nsp.name;
      this.sockets.delete(socket.id);
@@ -159,7 +160,7 @@ export class Client {
   *
   * @private
   */
-  private close() {
+  private close(): void {
    if ("open" === this.conn.readyState) {
      debug("forcing transport close");
      this.conn.close();
@@ -174,12 +175,13 @@ export class Client {
   * @param {Object} opts
   * @private
   */
-  _packet(packet, opts?) {
+  _packet(packet: Packet, opts?: any): void {
    opts = opts || {};
    const self = this;

    // this writes to the actual connection
-    function writeToEngine(encodedPackets) {
+    function writeToEngine(encodedPackets: any) {
+      // TODO clarify this.
      if (opts.volatile && !self.conn.transport.writable) return;
      for (let i = 0; i < encodedPackets.length; i++) {
        self.conn.write(encodedPackets[i], { compress: opts.compress });
@@ -205,7 +207,7 @@ export class Client {
   *
   * @private
   */
-  private ondata(data) {
+  private ondata(data): void {
    // try/catch is needed for protocol violations (GH-1880)
    try {
      this.decoder.add(data);
@@ -219,9 +221,14 @@ export class Client {
   *
   * @private
   */
-  private ondecoded(packet: Packet) {
+  private ondecoded(packet: Packet): void {
    if (PacketType.CONNECT === packet.type) {
-      this.connect(packet.nsp, packet.data);
+      if (this.conn.protocol === 3) {
+        const parsed = url.parse(packet.nsp, true);
+        this.connect(parsed.pathname!, parsed.query);
+      } else {
+        this.connect(packet.nsp, packet.data);
+      }
    } else {
      const socket = this.nsps.get(packet.nsp);
      if (socket) {
@@ -240,7 +247,7 @@ export class Client {
   * @param {Object} err object
   * @private
   */
-  private onerror(err) {
+  private onerror(err): void {
    for (const socket of this.sockets.values()) {
      socket._onerror(err);
    }
@@ -253,7 +260,7 @@ export class Client {
   * @param reason
   * @private
   */
-  private onclose(reason: string) {
+  private onclose(reason: string): void {
    debug("client close with reason %s", reason);

    // ignore a potential subsequent `close` event
@@ -272,7 +279,7 @@ export class Client {
   * Cleans up event listeners.
   * @private
   */
-  private destroy() {
+  private destroy(): void {
    this.conn.removeListener("data", this.ondata);
    this.conn.removeListener("error", this.onerror);
    this.conn.removeListener("close", this.onclose);
--- a/lib/index.ts
+++ b/lib/index.ts
@@ -25,7 +25,7 @@ const dotMapRegex = /\.map/;
 type Transport = "polling" | "websocket";
 type ParentNspNameMatchFn = (
  name: string,
-  query: object,
+  auth: { [key: string]: any },
  fn: (err: Error | null, success: boolean) => void
 ) => void;

@@ -191,6 +191,10 @@ export class Server extends EventEmitter {
   */
  constructor(opts?: Partial<ServerOptions>);
  constructor(srv?: http.Server | number, opts?: Partial<ServerOptions>);
+  constructor(
+    srv: undefined | Partial<ServerOptions> | http.Server | number,
+    opts?: Partial<ServerOptions>
+  );
  constructor(
    srv: undefined | Partial<ServerOptions> | http.Server | number,
    opts: Partial<ServerOptions> = {}
@@ -222,9 +226,10 @@ export class Server extends EventEmitter {
   * @return self when setting or value when getting
   * @public
   */
-  public serveClient(v: boolean): Server;
+  public serveClient(v: boolean): this;
  public serveClient(): boolean;
-  public serveClient(v?: boolean): Server | boolean {
+  public serveClient(v?: boolean): this | boolean;
+  public serveClient(v?: boolean): this | boolean {
    if (!arguments.length) return this._serveClient;
    this._serveClient = v!;
    return this;
@@ -234,16 +239,16 @@ export class Server extends EventEmitter {
   * Executes the middleware for an incoming namespace not already created on the server.
   *
   * @param name - name of incoming namespace
-   * @param {Object} auth - the auth parameters
+   * @param auth - the auth parameters
   * @param fn - callback
   *
   * @private
   */
  _checkNamespace(
    name: string,
-    auth: object,
+    auth: { [key: string]: any },
    fn: (nsp: Namespace | false) => void
-  ) {
+  ): void {
    if (this.parentNsps.size === 0) return fn(false);

    const keysIterator = this.parentNsps.keys();
@@ -272,9 +277,10 @@ export class Server extends EventEmitter {
   * @return {Server|String} self when setting or value when getting
   * @public
   */
-  public path(v: string): Server;
+  public path(v: string): this;
  public path(): string;
-  public path(v?: string): Server | string {
+  public path(v?: string): this | string;
+  public path(v?: string): this | string {
    if (!arguments.length) return this._path;

    this._path = v!.replace(/\/$/, "");
@@ -293,9 +299,10 @@ export class Server extends EventEmitter {
   * @param v
   * @public
   */
-  public connectTimeout(v: number): Server;
+  public connectTimeout(v: number): this;
  public connectTimeout(): number;
-  public connectTimeout(v?: number): Server | number {
+  public connectTimeout(v?: number): this | number;
+  public connectTimeout(v?: number): this | number {
    if (v === undefined) return this._connectTimeout;
    this._connectTimeout = v;
    return this;
@@ -309,8 +316,9 @@ export class Server extends EventEmitter {
   * @public
   */
  public adapter(): typeof Adapter | undefined;
-  public adapter(v: typeof Adapter): Server;
-  public adapter(v?: typeof Adapter): typeof Adapter | undefined | Server {
+  public adapter(v: typeof Adapter): this;
+  public adapter(v?: typeof Adapter): typeof Adapter | undefined | this;
+  public adapter(v?: typeof Adapter): typeof Adapter | undefined | this {
    if (!arguments.length) return this._adapter;
    this._adapter = v;
    for (const nsp of this._nsps.values()) {
@@ -330,7 +338,7 @@ export class Server extends EventEmitter {
  public listen(
    srv: http.Server | number,
    opts: Partial<ServerOptions> = {}
-  ): Server {
+  ): this {
    return this.attach(srv, opts);
  }

@@ -345,7 +353,7 @@ export class Server extends EventEmitter {
  public attach(
    srv: http.Server | number,
    opts: Partial<ServerOptions> = {}
-  ): Server {
+  ): this {
    if ("function" == typeof srv) {
      const msg =
        "You are trying to attach socket.io to an express " +
@@ -385,7 +393,10 @@ export class Server extends EventEmitter {
   * @param opts - options passed to engine.io
   * @private
   */
-  private initEngine(srv: http.Server, opts: Partial<EngineAttachOptions>) {
+  private initEngine(
+    srv: http.Server,
+    opts: Partial<EngineAttachOptions>
+  ): void {
    // initialize engine
    debug("creating engine.io instance with opts %j", opts);
    this.eio = engine.attach(srv, opts);
@@ -406,7 +417,7 @@ export class Server extends EventEmitter {
   * @param srv http server
   * @private
   */
-  private attachServe(srv: http.Server) {
+  private attachServe(srv: http.Server): void {
    debug("attaching client serving req handler");

    const evs = srv.listeners("request").slice(0);
@@ -429,7 +440,7 @@ export class Server extends EventEmitter {
   * @param res
   * @private
   */
-  private serve(req: http.IncomingMessage, res: http.ServerResponse) {
+  private serve(req: http.IncomingMessage, res: http.ServerResponse): void {
    const filename = req.url!.replace(this._path, "");
    const isMap = dotMapRegex.test(filename);
    const type = isMap ? "map" : "source";
@@ -474,7 +485,7 @@ export class Server extends EventEmitter {
    filename: string,
    req: http.IncomingMessage,
    res: http.ServerResponse
-  ) {
+  ): void {
    const readStream = createReadStream(
      path.join(__dirname, "../client-dist/", filename)
    );
@@ -513,7 +524,7 @@ export class Server extends EventEmitter {
   * @return self
   * @public
   */
-  public bind(engine): Server {
+  public bind(engine): this {
    this.engine = engine;
    this.engine.on("connection", this.onconnection.bind(this));
    return this;
@@ -526,7 +537,7 @@ export class Server extends EventEmitter {
   * @return self
   * @private
   */
-  private onconnection(conn): Server {
+  private onconnection(conn): this {
    debug("incoming connection with id %s", conn.id);
    const client = new Client(this, conn);
    if (conn.protocol === 3) {
@@ -540,13 +551,13 @@ export class Server extends EventEmitter {
   * Looks up a namespace.
   *
   * @param {String|RegExp|Function} name nsp name
-   * @param [fn] optional, nsp `connection` ev handler
+   * @param fn optional, nsp `connection` ev handler
   * @public
   */
  public of(
    name: string | RegExp | ParentNspNameMatchFn,
    fn?: (socket: Socket) => void
-  ) {
+  ): Namespace {
    if (typeof name === "function" || name instanceof RegExp) {
      const parentNsp = new ParentNamespace(this);
      debug("initializing parent namespace %s", parentNsp.name);
@@ -605,7 +616,7 @@ export class Server extends EventEmitter {
   */
  public use(
    fn: (socket: Socket, next: (err?: ExtendedError) => void) => void
-  ): Server {
+  ): this {
    this.sockets.use(fn);
    return this;
  }
@@ -617,7 +628,7 @@ export class Server extends EventEmitter {
   * @return self
   * @public
   */
-  public to(name: Room): Server {
+  public to(name: Room): this {
    this.sockets.to(name);
    return this;
  }
@@ -629,7 +640,7 @@ export class Server extends EventEmitter {
   * @return self
   * @public
   */
-  public in(name: Room): Server {
+  public in(name: Room): this {
    this.sockets.in(name);
    return this;
  }
@@ -640,7 +651,7 @@ export class Server extends EventEmitter {
   * @return self
   * @public
   */
-  public send(...args: readonly any[]): Server {
+  public send(...args: readonly any[]): this {
    this.sockets.emit("message", ...args);
    return this;
  }
@@ -651,7 +662,7 @@ export class Server extends EventEmitter {
   * @return self
   * @public
   */
-  public write(...args: readonly any[]): Server {
+  public write(...args: readonly any[]): this {
    this.sockets.emit("message", ...args);
    return this;
  }
@@ -672,7 +683,7 @@ export class Server extends EventEmitter {
   * @return self
   * @public
   */
-  public compress(compress: boolean): Server {
+  public compress(compress: boolean): this {
    this.sockets.compress(compress);
    return this;
  }
@@ -685,7 +696,7 @@ export class Server extends EventEmitter {
   * @return self
   * @public
   */
-  public get volatile(): Server {
+  public get volatile(): this {
    this.sockets.volatile;
    return this;
  }
@@ -696,7 +707,7 @@ export class Server extends EventEmitter {
   * @return self
   * @public
   */
-  public get local(): Server {
+  public get local(): this {
    this.sockets.local;
    return this;
  }
--- a/lib/namespace.ts
+++ b/lib/namespace.ts
@@ -67,7 +67,7 @@ export class Namespace extends EventEmitter {
   */
  public use(
    fn: (socket: Socket, next: (err?: ExtendedError) => void) => void
-  ): Namespace {
+  ): this {
    this._fns.push(fn);
    return this;
  }
@@ -106,7 +106,7 @@ export class Namespace extends EventEmitter {
   * @return self
   * @public
   */
-  public to(name: Room): Namespace {
+  public to(name: Room): this {
    this._rooms.add(name);
    return this;
  }
@@ -118,7 +118,7 @@ export class Namespace extends EventEmitter {
   * @return self
   * @public
   */
-  public in(name: Room): Namespace {
+  public in(name: Room): this {
    this._rooms.add(name);
    return this;
  }
@@ -222,7 +222,7 @@ export class Namespace extends EventEmitter {
   * @return self
   * @public
   */
-  public send(...args: readonly any[]): Namespace {
+  public send(...args: readonly any[]): this {
    this.emit("message", ...args);
    return this;
  }
@@ -233,7 +233,7 @@ export class Namespace extends EventEmitter {
   * @return self
   * @public
   */
-  public write(...args: readonly any[]): Namespace {
+  public write(...args: readonly any[]): this {
    this.emit("message", ...args);
    return this;
  }
@@ -262,7 +262,7 @@ export class Namespace extends EventEmitter {
   * @return self
   * @public
   */
-  public compress(compress: boolean): Namespace {
+  public compress(compress: boolean): this {
    this._flags.compress = compress;
    return this;
  }
@@ -275,7 +275,7 @@ export class Namespace extends EventEmitter {
   * @return self
   * @public
   */
-  public get volatile(): Namespace {
+  public get volatile(): this {
    this._flags.volatile = true;
    return this;
  }
@@ -286,7 +286,7 @@ export class Namespace extends EventEmitter {
   * @return self
   * @public
   */
-  public get local(): Namespace {
+  public get local(): this {
    this._flags.local = true;
    return this;
  }
--- a/lib/socket.ts
+++ b/lib/socket.ts
@@ -1,11 +1,11 @@
 import { EventEmitter } from "events";
-import { PacketType } from "socket.io-parser";
+import { Packet, PacketType } from "socket.io-parser";
 import url = require("url");
 import debugModule from "debug";
 import type { Server } from "./index";
 import type { Client } from "./client";
 import type { Namespace } from "./namespace";
-import type { IncomingMessage } from "http";
+import type { IncomingMessage, IncomingHttpHeaders } from "http";
 import type {
  Adapter,
  BroadcastFlags,
@@ -13,6 +13,7 @@ import type {
  SocketId,
 } from "socket.io-adapter";
 import base64id from "base64id";
+import type { ParsedUrlQuery } from "querystring";

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

@@ -33,7 +34,7 @@ export interface Handshake {
  /**
   * The headers sent as part of the handshake
   */
-  headers: object;
+  headers: IncomingHttpHeaders;

  /**
   * The date of creation (as string)
@@ -68,12 +69,12 @@ export interface Handshake {
  /**
   * The query object
   */
-  query: object;
+  query: ParsedUrlQuery;

  /**
   * The auth object
   */
-  auth: object;
+  auth: { [key: string]: any };
 }

 export class Socket extends EventEmitter {
@@ -190,7 +191,7 @@ export class Socket extends EventEmitter {
   * @return self
   * @public
   */
-  public to(name: Room): Socket {
+  public to(name: Room): this {
    this._rooms.add(name);
    return this;
  }
@@ -202,7 +203,7 @@ export class Socket extends EventEmitter {
   * @return self
   * @public
   */
-  public in(name: Room): Socket {
+  public in(name: Room): this {
    this._rooms.add(name);
    return this;
  }
@@ -213,7 +214,7 @@ export class Socket extends EventEmitter {
   * @return self
   * @public
   */
-  public send(...args: readonly any[]): Socket {
+  public send(...args: readonly any[]): this {
    this.emit("message", ...args);
    return this;
  }
@@ -224,7 +225,7 @@ export class Socket extends EventEmitter {
   * @return self
   * @public
   */
-  public write(...args: readonly any[]): Socket {
+  public write(...args: readonly any[]): this {
    this.emit("message", ...args);
    return this;
  }
@@ -236,10 +237,13 @@ export class Socket extends EventEmitter {
   * @param {Object} opts - options
   * @private
   */
-  private packet(packet, opts: any = {}) {
+  private packet(
+    packet: Omit<Packet, "nsp"> & Partial<Pick<Packet, "nsp">>,
+    opts: any = {}
+  ): void {
    packet.nsp = this.nsp.name;
    opts.compress = false !== opts.compress;
-    this.client._packet(packet, opts);
+    this.client._packet(packet as Packet, opts);
  }

  /**
@@ -304,7 +308,7 @@ export class Socket extends EventEmitter {
   * @param {Object} packet
   * @private
   */
-  _onpacket(packet) {
+  _onpacket(packet: Packet): void {
    debug("got packet %j", packet);
    switch (packet.type) {
      case PacketType.EVENT:
@@ -335,10 +339,10 @@ export class Socket extends EventEmitter {
  /**
   * Called upon event packet.
   *
-   * @param {Object} packet - packet object
+   * @param {Packet} packet - packet object
   * @private
   */
-  private onevent(packet): void {
+  private onevent(packet: Packet): void {
    const args = packet.data || [];
    debug("emitting event %j", args);

@@ -362,7 +366,7 @@ export class Socket extends EventEmitter {
   * @param {Number} id - packet id
   * @private
   */
-  private ack(id: number) {
+  private ack(id: number): () => void {
    const self = this;
    let sent = false;
    return function () {
@@ -386,12 +390,12 @@ export class Socket extends EventEmitter {
   *
   * @private
   */
-  private onack(packet): void {
-    const ack = this.acks.get(packet.id);
+  private onack(packet: Packet): void {
+    const ack = this.acks.get(packet.id!);
    if ("function" == typeof ack) {
      debug("calling ack %s with %j", packet.id, packet.data);
      ack.apply(this, packet.data);
-      this.acks.delete(packet.id);
+      this.acks.delete(packet.id!);
    } else {
      debug("bad ack %s", packet.id);
    }
@@ -429,7 +433,7 @@ export class Socket extends EventEmitter {
   *
   * @private
   */
-  _onclose(reason: string): Socket | undefined {
+  _onclose(reason: string): this | undefined {
    if (!this.connected) return this;
    debug("closing socket - reason %s", reason);
    super.emit("disconnecting", reason);
@@ -449,7 +453,7 @@ export class Socket extends EventEmitter {
   *
   * @private
   */
-  _error(err) {
+  _error(err): void {
    this.packet({ type: PacketType.CONNECT_ERROR, data: err });
  }

@@ -461,7 +465,7 @@ export class Socket extends EventEmitter {
   *
   * @public
   */
-  public disconnect(close = false): Socket {
+  public disconnect(close = false): this {
    if (!this.connected) return this;
    if (close) {
      this.client._disconnect();
@@ -479,7 +483,7 @@ export class Socket extends EventEmitter {
   * @return {Socket} self
   * @public
   */
-  public compress(compress: boolean): Socket {
+  public compress(compress: boolean): this {
    this.flags.compress = compress;
    return this;
  }
@@ -492,7 +496,7 @@ export class Socket extends EventEmitter {
   * @return {Socket} self
   * @public
   */
-  public get volatile(): Socket {
+  public get volatile(): this {
    this.flags.volatile = true;
    return this;
  }
@@ -504,7 +508,7 @@ export class Socket extends EventEmitter {
   * @return {Socket} self
   * @public
   */
-  public get broadcast(): Socket {
+  public get broadcast(): this {
    this.flags.broadcast = true;
    return this;
  }
@@ -515,7 +519,7 @@ export class Socket extends EventEmitter {
   * @return {Socket} self
   * @public
   */
-  public get local(): Socket {
+  public get local(): this {
    this.flags.local = true;
    return this;
  }
@@ -526,14 +530,18 @@ export class Socket extends EventEmitter {
   * @param {Array} event - event that will get emitted
   * @private
   */
-  private dispatch(event): void {
+  private dispatch(event: [eventName: string, ...args: any[]]): void {
    debug("dispatching an event %j", event);
    this.run(event, (err) => {
      process.nextTick(() => {
        if (err) {
          return this._onerror(err);
        }
-        super.emit.apply(this, event);
+        if (this.connected) {
+          super.emit.apply(this, event);
+        } else {
+          debug("ignore packet received after disconnection");
+        }
      });
    });
  }
@@ -547,7 +555,7 @@ export class Socket extends EventEmitter {
   */
  public use(
    fn: (event: Array<any>, next: (err: Error) => void) => void
-  ): Socket {
+  ): this {
    this.fns.push(fn);
    return this;
  }
@@ -559,11 +567,14 @@ export class Socket extends EventEmitter {
   * @param {Function} fn - last fn call in the middleware
   * @private
   */
-  private run(event: Array<any>, fn: (err: Error | null) => void) {
+  private run(
+    event: [eventName: string, ...args: any[]],
+    fn: (err: Error | null) => void
+  ): void {
    const fns = this.fns.slice(0);
    if (!fns.length) return fn(null);

-    function run(i) {
+    function run(i: number) {
      fns[i](event, function (err) {
        // upon error, short-circuit
        if (err) return fn(err);
@@ -611,7 +622,7 @@ export class Socket extends EventEmitter {
   * @param listener
   * @public
   */
-  public onAny(listener: (...args: any[]) => void): Socket {
+  public onAny(listener: (...args: any[]) => void): this {
    this._anyListeners = this._anyListeners || [];
    this._anyListeners.push(listener);
    return this;
@@ -624,7 +635,7 @@ export class Socket extends EventEmitter {
   * @param listener
   * @public
   */
-  public prependAny(listener: (...args: any[]) => void): Socket {
+  public prependAny(listener: (...args: any[]) => void): this {
    this._anyListeners = this._anyListeners || [];
    this._anyListeners.unshift(listener);
    return this;
@@ -636,7 +647,7 @@ export class Socket extends EventEmitter {
   * @param listener
   * @public
   */
-  public offAny(listener?: (...args: any[]) => void): Socket {
+  public offAny(listener?: (...args: any[]) => void): this {
    if (!this._anyListeners) {
      return this;
    }
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
  "name": "socket.io",
-  "version": "3.1.0",
+  "version": "3.1.2",
  "lockfileVersion": 1,
  "requires": true,
  "dependencies": {
@@ -874,9 +874,9 @@
      }
    },
    "engine.io-client": {
-      "version": "4.1.0",
-      "resolved": "https://registry.npmjs.org/engine.io-client/-/engine.io-client-4.1.0.tgz",
-      "integrity": "sha512-OUmn4m71/lW3ixICv4h3DuBRuh3ri0w3cDuepjsrINSbbqbni4Xw1shTFiKhl0v58lEtNpwJTpSKJJ3fondu5Q==",
+      "version": "4.1.2",
+      "resolved": "https://registry.npmjs.org/engine.io-client/-/engine.io-client-4.1.2.tgz",
+      "integrity": "sha512-1mwvwKYMa0AaCy+sPgvJ/SnKyO5MJZ1HEeXfA3Rm/KHkHGiYD5bQVq8QzvIrkI01FuVtOdZC5lWdRw1BGXB2NQ==",
      "dev": true,
      "requires": {
        "base64-arraybuffer": "0.1.4",
@@ -2258,9 +2258,9 @@
      "integrity": "sha512-+vDov/aTsLjViYTwS9fPy5pEtTkrbEKsw2M+oVSoFGw6OD1IpvlV1VPhUzNbofCQ8oyMbdYJqDtGdmHQK6TdPg=="
    },
    "socket.io-client": {
-      "version": "3.1.0",
-      "resolved": "https://registry.npmjs.org/socket.io-client/-/socket.io-client-3.1.0.tgz",
-      "integrity": "sha512-T4qPOL80KnoBwkdR70zMpiR6aH6zv3ZqLNriofHqsO9wvQllNTOez0mpV4GdVqo1Y55Z+h8YOlBo7c8pOxDlHw==",
+      "version": "3.1.2",
+      "resolved": "https://registry.npmjs.org/socket.io-client/-/socket.io-client-3.1.2.tgz",
+      "integrity": "sha512-fXhF8plHrd7U14A7K0JPOmZzpmGkLpIS6623DzrBZqYzI/yvlP4fA3LnxwthEVgiHmn2uJ4KjdnQD8A03PuBWQ==",
      "dev": true,
      "requires": {
        "@types/component-emitter": "^1.2.10",
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
  "name": "socket.io",
-  "version": "3.1.0",
+  "version": "3.1.2",
  "description": "node.js realtime framework server",
  "keywords": [
    "realtime",
@@ -45,7 +45,7 @@
  "dependencies": {
    "@types/cookie": "^0.4.0",
    "@types/cors": "^2.8.8",
-    "@types/node": "^14.14.10",
+    "@types/node": ">=10.0.0",
    "accepts": "~1.3.4",
    "base64id": "~2.0.0",
    "debug": "~4.3.1",
@@ -63,7 +63,7 @@
    "nyc": "^15.1.0",
    "prettier": "^2.2.0",
    "rimraf": "^3.0.2",
-    "socket.io-client": "3.1.0",
+    "socket.io-client": "3.1.2",
    "socket.io-client-v2": "npm:socket.io-client@^2.4.0",
    "superagent": "^6.1.0",
    "supertest": "^6.0.1",
--- a/test/socket.io.ts
+++ b/test/socket.io.ts
@@ -1787,6 +1787,33 @@ describe("socket.io", () => {
      });
    });

+    it("should ignore a packet received after disconnection", (done) => {
+      const srv = createServer();
+      const sio = new Server(srv);
+
+      srv.listen(() => {
+        const clientSocket = client(srv);
+
+        const success = () => {
+          clientSocket.close();
+          sio.close();
+          done();
+        };
+
+        sio.on("connection", (socket) => {
+          socket.on("test", () => {
+            done(new Error("should not happen"));
+          });
+          socket.on("disconnect", success);
+        });
+
+        clientSocket.on("connect", () => {
+          clientSocket.emit("test", Buffer.alloc(10));
+          clientSocket.disconnect();
+        });
+      });
+    });
+
    describe("onAny", () => {
      it("should call listener", (done) => {
        const srv = createServer();
@@ -2479,6 +2506,32 @@ describe("socket.io", () => {
      });
    });

+    it("should be able to connect to a namespace with a query", (done) => {
+      const srv = createServer();
+      const sio = new Server(srv, {
+        allowEIO3: true,
+      });
+
+      srv.listen(async () => {
+        const port = (srv.address() as AddressInfo).port;
+        const clientSocket = io_v2.connect(
+          `http://localhost:${port}/the-namespace`,
+          {
+            multiplex: false,
+          }
+        );
+        clientSocket.query = { test: "123" };
+
+        const [socket]: Array<any> = await Promise.all([
+          waitFor(sio.of("/the-namespace"), "connection"),
+          waitFor(clientSocket, "connect"),
+        ]);
+
+        expect(socket.handshake.auth).to.eql({ test: "123" });
+        success(sio, clientSocket, done);
+      });
+    });
+
    it("should not connect if `allowEIO3` is false (default)", (done) => {
      const srv = createServer();
      const sio = new Server(srv);
Author	SHA1	Message	Date
Damien Arrachequesne	225ade062a	chore(release): 3.1.2 Diff: https://github.com/socketio/socket.io/compare/3.1.1...3.1.2	2021-02-26 01:18:42 +01:00
Damien Arrachequesne	494c64e44f	fix: ignore packet received after disconnection Related: https://github.com/socketio/socket.io/issues/3095	2021-02-26 00:58:30 +01:00
Damien Arrachequesne	67a61e39e6	chore: loosen the version requirement of @types/node Related: https://github.com/socketio/socket.io/issues/3793	2021-02-26 00:58:01 +01:00
Damien Arrachequesne	7467216e02	docs(examples): 4th and final part of the "private messaging" example See also: https://socket.io/get-started/private-messaging-part-4/	2021-02-17 00:24:23 +01:00
Damien Arrachequesne	7247b4051f	docs(examples): 3rd part of the "private messaging" example See also: https://socket.io/get-started/private-messaging-part-3/	2021-02-17 00:22:55 +01:00
Damien Arrachequesne	992c9380c3	docs(examples): 2nd part of the "private messaging" example See also: https://socket.io/get-started/private-messaging-part-2/	2021-02-15 01:09:12 +01:00
Damien Arrachequesne	8b404f424b	docs(examples): 1st part of the "private messaging" example	2021-02-10 00:33:39 +01:00
Damien Arrachequesne	12221f296d	chore(release): 3.1.1 Diff: https://github.com/socketio/socket.io/compare/3.1.0...3.1.1	2021-02-03 22:57:21 +01:00
Damien Arrachequesne	6f4bd7f8e7	fix: properly parse the CONNECT packet in v2 compatibility mode In Socket.IO v2, the Socket query option was appended to the namespace in the CONNECT packet: { type: 0, nsp: "/my-namespace?abc=123" } Note: the "query" option on the client-side (v2) will be found in the "auth" attribute on the server-side: ``` // client-side const socket = io("/nsp1", { query: { abc: 123 } }); socket.query = { abc: 456 }; // server-side const io = require("socket.io")(httpServer, { allowEIO3: true // enable compatibility mode }); io.of("/nsp1").on("connection", (socket) => { console.log(socket.handshake.auth); // { abc: 456 } (the Socket query) console.log(socket.handshake.query.abc); // 123 (the Manager query) }); More information here: https://socket.io/docs/v3/migrating-from-2-x-to-3-0/#Add-a-clear-distinction-between-the-Manager-query-option-and-the-Socket-query-option Related: https://github.com/socketio/socket.io/issues/3791	2021-02-03 22:54:07 +01:00
Damien Arrachequesne	4f2e9a716d	fix(typings): update the types of "query", "auth" and "headers" Related: https://github.com/socketio/socket.io/issues/3770	2021-02-03 22:53:38 +01:00
david-fong	9e8f288ca9	fix(typings): add return types and general-case overload signatures (#3776 ) See also: https://stackoverflow.com/questions/52760509/typescript-returntype-of-overloaded-function/52760599#52760599	2021-02-02 11:50:08 +01:00
Damien Arrachequesne	86eb4227b2	docs(examples): add example with traefik Reference: https://doc.traefik.io/traefik/v2.0/	2021-01-31 23:47:23 +01:00
Damien Arrachequesne	cf873fd831	docs(examples): update cluster examples to Socket.IO v3	2021-01-28 11:21:38 +01:00
Damien Arrachequesne	0d10e6131b	docs(examples): update the nginx cluster example Related: https://github.com/socketio/socket.io/discussions/3778 Reference: http://nginx.org/en/docs/http/ngx_http_upstream_module.html#hash	2021-01-28 10:52:26 +01:00
JPSO	10aafbbc16	ci: add Node.js 15 (#3765 )	2021-01-20 22:34:51 +01:00
Hamdi Bayhan	f34cfca26d	docs: fix broken link (#3759 )	2021-01-17 22:10:37 +01:00
PrashoonB	d412e876b8	docs: add installation with yarn (#3757 )	2021-01-15 22:20:04 +01:00