4.6.1

Bug Fixes

• properly handle manually created dynamic namespaces (0d0a7a2)
• types: fix nodenext module resolution compatibility (#4625) (d0b22c6)

Links

• Diff: 4.6.0...4.6.1
• Client release: 4.6.1
• engine.io@~6.4.1 (diff)
• ws@~8.11.0 (no change)

4.6.0

Bug Fixes

• add timeout method to remote socket (#4558) (0c0eb00)
• typings: properly type emits with timeout (f3ada7d)

Features

Promise-based acknowledgements

This commit adds some syntactic sugar around acknowledgements:

• emitWithAck()

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()

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.

Connection state recovery

This feature allows a client to reconnect after a temporary disconnection and restore its state:

• id
• rooms
• data
• missed packets

Usage:

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, which will support this feature.

Added in 54d5ee0.

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:

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.

Error details in the disconnecting and disconnect events

The disconnect event will now contain additional details about the disconnection reason.

io.on("connection", (socket) => {
  socket.on("disconnect", (reason, description) => {
    console.log(description);
  });
});

Added in 8aa9499.

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.

import { createServer } from "node:http";
import { Server } from "socket.io";

const httpServer = createServer();
const io = new Server(httpServer, {
  cleanupEmptyChildNamespaces: true
});

Added in 5d9220b.

A new "addTrailingSlash" option

The trailing slash which was added by default can now be disabled:

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.

Performance Improvements

• precompute the WebSocket frames when broadcasting (da2b542)

Links:

• Diff: 4.5.4...4.6.0
• Client release: 4.6.0
• engine.io@~6.4.0 (diff)
• ws@~8.11.0 (diff)

4.5.4

This release contains a bump of:

• engine.io in order to fix CVE-2022-41940
• socket.io-parser in order to fix CVE-2022-2421.

Links:

• Diff: 4.5.3...4.5.4
• Client release: 4.5.4
• engine.io@~6.2.1 (diff)
• ws@~8.2.3

4.5.3

Bug Fixes

• typings: accept an HTTP2 server in the constructor (d3d0a2d)
• typings: apply types to "io.timeout(...).emit()" calls (e357daf)

Links:

• Diff: 4.5.2...4.5.3
• Client release: 4.5.3
• engine.io version: ~6.2.0
• ws version: ~8.2.3

4.5.2

Bug Fixes

• prevent the socket from joining a room after disconnection (18f3fda)
• uws: prevent the server from crashing after upgrade (ba497ee)

Links:

• Diff: 4.5.1...4.5.2
• Client release: 4.5.2
• engine.io version: ~6.2.0
• ws version: ~8.2.3

2.5.0

⚠️ WARNING ⚠️

The default value of the maxHttpBufferSize option has been decreased from 100 MB to 1 MB, in order to prevent attacks by denial of service.

Security advisory: GHSA-j4f2-536g-r55m

Bug Fixes

• fix race condition in dynamic namespaces (05e1278)
• ignore packet received after disconnection (22d4bdf)
• only set 'connected' to true after middleware execution (226cc16)
• prevent the socket from joining a room after disconnection (f223178)

Links:

• Diff: 2.4.1...2.5.0
• Client release: 2.5.0
• engine.io version: ~3.6.0 (diff)
• ws version: ~7.4.2

4.5.1

Bug Fixes

• forward the local flag to the adapter when using fetchSockets() (30430f0)
• typings: add HTTPS server to accepted types (#4351) (9b43c91)

Links:

• Diff: 4.5.0...4.5.1
• Client release: 4.5.1
• engine.io version: ~6.2.0
• ws version: ~8.2.3

4.5.0

Bug Fixes

• typings: ensure compatibility with TypeScript 3.x (#4259) (02c87a8)

Features

• add support for catch-all listeners for outgoing packets (531104d)

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

Syntax:

socket.onAnyOutgoing((event, ...args) => {
  console.log(event);
});

• broadcast and expect multiple acks (8b20457)

Syntax:

io.timeout(1000).emit("some-event", (err, responses) => {
  // ...
});

• add the "maxPayload" field in the handshake details (088dcb4)

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}

Links:

• Diff: 4.4.1...4.5.0
• Client release: 4.5.0
• engine.io version: ~6.2.0 (diff)
• ws version: ~8.2.3

4.4.1

Bug Fixes

• types: make RemoteSocket.data type safe (#4234) (770ee59)
• types: pass SocketData type to custom namespaces (#4233) (f2b8de7)

Links:

• Diff: 4.4.0...4.4.1
• Client release: 4.4.1
• engine.io version: ~6.1.0 (diff)
• ws version: ~8.2.3

4.4.0

Bug Fixes

• only set 'connected' to true after middleware execution (02b0f73)

Features

• add an implementation based on uWebSockets.js (c0d8c5a)

const { App } = require("uWebSockets.js");
const { Server } = require("socket.io");

const app = new App();
const io = new Server();

io.attachApp(app);

io.on("connection", (socket) => {
  // ...
});

app.listen(3000, (token) => {
  if (!token) {
    console.warn("port already in use");
  }
});

• add timeout feature (f0ed42f)

socket.timeout(5000).emit("my-event", (err) => {
  if (err) {
    // the client did not acknowledge the event in the given delay
  }
});

• add type information to socket.data (#4159) (fe8730c)

interface SocketData {
  name: string;
  age: number;
}

const io = new Server<ClientToServerEvents, ServerToClientEvents, InterServerEvents, SocketData>();

io.on("connection", (socket) => {
  socket.data.name = "john";
  socket.data.age = 42;
});

Links:

• Diff: 4.3.2...4.4.0
• Client release: 4.4.0
• engine.io version: ~6.1.0 (diff)
• ws version: ~8.2.3