socket.io

Bug Fixes

• Cleanup pending acks on timeout to prevent memory leak

• Prevent uWebSockets.js from serving missing client files

• Reject stateful regexps for dynamic namespaces

• types: allow emitWithAck() for events with void callbacks

• types: properly import http module

Bug Fixes

• Do not throw when calling io.close() on a stopped server

The url.parse() function is now deprecated and has been replaced by new URL() (see 8af7019).

Bug Fixes

• Call adapter.init() when creating each namespace

• Improve io.close() function

Due to a change in the bundler configuration, the production bundle (socket.io.min.js) did not support sending and receiving binary data in version 4.8.0. This is now fixed.

Bug Fixes

• Allow to join a room in a middleware (uws)

• Correctly await async close on adapters

• Expose type of default engine

Bug Fixes

• Close the adapters when the server is closed

• Remove duplicate pipeline when serving bundle

Bug Fixes

• typings: calling io.emit with no arguments incorrectly errored (cb6d2e0), closes #4914

Bug Fixes

• Return the first response when broadcasting to a single socket

• typings: allow to bind to a non-secure Http2Server

Bug Fixes

• Clean up child namespace when client is rejected in middleware

• webtransport: properly handle WebTransport-only connections

• webtransport: add proper framing

The client bundle contains a few fixes regarding the WebTransport support.

Bug Fixes

• Remove the Partial modifier from the socket.data type

Features

Support for WebTransport

The Socket.IO server can now use WebTransport as the underlying transport.

WebTransport is a web API that uses the HTTP/3 protocol as a bidirectional transport. It's intended for two-way communications between a web client and an HTTP/3 server.

References:

Until WebTransport support lands in Node.js, you can use the @fails-components/webtransport package:

import { readFileSync } from "fs";
import { createServer } from "https";
import { Server } from "socket.io";
import { Http3Server } from "@fails-components/webtransport";

// WARNING: the total length of the validity period MUST NOT exceed two weeks (https://w3c.github.io/webtransport/#custom-certificate-requirements)
const cert = readFileSync("/path/to/my/cert.pem");
const key = readFileSync("/path/to/my/key.pem");

const httpsServer = createServer({
  key,
  cert
});

httpsServer.listen(3000);

const io = new Server(httpsServer, {
  transports: ["polling", "websocket", "webtransport"] // WebTransport is not enabled by default
});

const h3Server = new Http3Server({
  port: 3000,
  host: "0.0.0.0",
  secret: "changeit",
  cert,
  privKey: key,
});

(async () => {
  const stream = await h3Server.sessionStream("/socket.io/");
  const sessionReader = stream.getReader();

  while (true) {
    const { done, value } = await sessionReader.read();
    if (done) {
      break;
    }
    io.engine.onWebTransportSession(value);
  }
})();

h3Server.startServer();

Added in 123b68c.

Client bundles with CORS headers

The bundles will now have the right Access-Control-Allow-xxx headers.

Added in 63f181c.

Bug Fixes

• exports: move types condition to the top

Bug Fixes

• Properly handle manually created dynamic namespaces

• types: fix nodenext module resolution compatibility

Bug Fixes

• Add timeout method to remote socket

• typings: properly type emits with timeout

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

This release contains a bump of:

• security

  engine.io in order to fix CVE-2022-41940

• security

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

Bug Fixes

• typings: accept an HTTP2 server in the constructor

• typings: apply types to "io.timeout(...).emit()" calls

Bug Fixes

• typings: ensure compatibility with TypeScript 3.x

Features

Catch-all listeners for outgoing packets

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

Syntax:

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

Added in 531104d.

Broadcast and expect multiple acknowledgements

Syntax:

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

Added in 8b20457.

maxHttpBufferSize value negotiation

A "maxPayload" field is now included in the Engine.IO handshake, so that clients in HTTP long-polling can decide how many packets they have to send to stay under the maxHttpBufferSize value.

This is a backward compatible change which should not mandate a new major revision of the protocol (we stay in v4), as we only add a field in the JSON-encoded handshake data:

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

Added in 088dcb4.

Bug Fixes

• Only set 'connected' to true after middleware execution

Features

• Add an implementation based on uWebSockets.js

• Add timeout feature

• Add type information to socket.data

Features

• Add support for inter-server communication

• Notify upon namespace creation

• Add a "connection_error" event (7096e98, from engine.io)

• Add the "initial_headers" and "headers" events (2527543, from engine.io)

Performance Improvements

• Add support for the "wsPreEncoded" writing option

Bug Fixes

• Make io.to(...) immutable

Features

• Add some utility methods

• Add support for typed events

• Allow to exclude specific rooms when broadcasting

• Allow to pass an array to io.to(...)