4.7.5

Bug Fixes

• close the adapters when the server is closed (bf64870)
• remove duplicate pipeline when serving bundle (e426f3e)

Links

• Diff: 4.7.4...4.7.5
• Client release: 4.7.5
• engine.io@~6.5.2 (no change)
• ws@~8.11.0 (no change)

4.7.4

Bug Fixes

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

Links

• Diff: 4.7.3...4.7.4
• Client release: 4.7.4
• engine.io@~6.5.2 (no change)
• ws@~8.11.0 (no change)

4.7.3

Bug Fixes

• return the first response when broadcasting to a single socket (#4878) (df8e70f)
• typings: allow to bind to a non-secure Http2Server (#4853) (8c9ebc3)

Links

• Diff: 4.7.2...4.7.3
• Client release: 4.7.3
• engine.io@~6.5.2 (no change)
• ws@~8.11.0 (no change)

4.7.2

Bug Fixes

• clean up child namespace when client is rejected in middleware (#4773) (0731c0d)
• webtransport: properly handle WebTransport-only connections (3468a19)
• webtransport: add proper framing (a306db0)

Links

• Diff: 4.7.1...4.7.2
• Client release: 4.7.2
• engine.io@~6.5.2 (diff)
• ws@~8.11.0 (no change)

4.7.1

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

Links

• Diff: 4.7.0...4.7.1
• Client release: 4.7.1
• engine.io@~6.5.0 (no change)
• ws@~8.11.0 (no change)

4.7.0

Bug Fixes

• remove the Partial modifier from the socket.data type (#4740) (e5c62ca)

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:

• https://w3c.github.io/webtransport/
• https://developer.mozilla.org/en-US/docs/Web/API/WebTransport
• https://developer.chrome.com/articles/webtransport/

Until WebTransport support lands in Node.js, 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.

Links

• Diff: 4.6.2...4.7.0
• Client release: 4.7.0
• engine.io@~6.5.0 (diff)
• ws@~8.11.0 (no change)

4.6.2

Bug Fixes

• exports: move types condition to the top (#4698) (3d44aae)

Links

• Diff: 4.6.1...4.6.2
• Client release: 4.6.2
• engine.io@~6.4.2 (diff)
• ws@~8.11.0 (no change)

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