Bug Fixes

• discard acknowledgements upon disconnection (34cbfbb)

Links

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

There were some minor bug fixes on the server side, which mandate a client bump.

Links

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

Bug Fixes

• improve compatibility with node16 module resolution (#1595) (605de78)
• typings: accept string | undefined as init argument (5a3eafe)
• typings: fix the type of the socket#id attribute (f9c16f2)

Links

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

Some bug fixes are included from theengine.io-client package:

• webtransport: add proper framing (d55c39e)
• webtransport: honor the binaryType attribute (8270e00)

Links

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

Some bug fixes are included from theengine.io-client package:

• make closeOnBeforeunload default to false (a63066b)
• webtransport: properly handle abruptly closed connections (cf6aa1f)

Links

• Diff:4.7.0...4.7.1
• Server release:4.7.1
• engine.io-client@~6.5.1 (diff)
• ws@~8.11.0 (no change)

Bug Fixes

• properly report timeout error when connecting (5bc94b5)
• use same scope for setTimeout and clearTimeout calls (#1568) (f2892ab)

Features

Support for WebTransport

The Engine.IO client 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/

For Node.js clients: until WebTransport support landsin Node.js, you can use the@fails-components/webtransport package:

import{WebTransport}from"@fails-components/webtransport";global.WebTransport=WebTransport;

Added in7195c0f.

Cookie management for the Node.js client

When setting thewithCredentials option totrue, the Node.js client will now include the cookies in the HTTP requests, making it easier to use it with cookie-based sticky sessions.

import{io}from"socket.io-client";constsocket=io("https://example.com",{withCredentials:true});

Added in5fc88a6.

Conditional import of the ESM build with debug logs

By default, the ESM build does not include thedebug package in the browser environments, because it increases the bundle size (see16b6569).

Which means that, unfortunately, debug logs are not available in the devtools console, even when setting thelocalStorage.debug = ... attribute.

You can now import the build which includes thedebug packages with aconditional import. Example with vite:

import{defineConfig}from'vite'importreactfrom'@vitejs/plugin-react'exportdefaultdefineConfig({plugins:[react()],server:{port:4000},resolve:{conditions:["development"]}})

Reference:https://v2.vitejs.dev/config/#resolve-conditions

Added in781d753.

Links

• Diff:4.6.2...4.7.0
• Server release:4.7.0
• engine.io-client version:~6.5.0 (diff)
• ws version:~8.11.0 (no change)

Bug Fixes

• exports: movetypes condition to the top (#1580) (7ead241)

Links

• Diff:4.6.1...4.6.2
• Server release:4.6.2
• engine.io-client version:~6.4.0 (no change)
• ws version:~8.11.0 (no change)

Bug Fixes

• do not drain the queue while the socket is offline (4996f9e)
• prevent duplicate connections when multiplexing (46213a6)

Links

• Diff:4.6.0...4.6.1
• Server release:4.6.1
• engine.io-client version:~6.4.0 (no change)
• ws version:~8.11.0 (no change)

Bug Fixes

• typings: do not expose browser-specific types (4d6d95e)
• ensure manager.socket() returns an active socket (b7dd891)
• typings: properly type emits with timeout (#1570) (33e4172)

Features

A new "addTrailingSlash" option

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

import{io}from"socket.io-client";constsocket=io("https://example.com",{addTrailingSlash:false});

In the example above, the request URL will behttps://example.com/socket.io instead ofhttps://example.com/socket.io/.

Added in21a6e12.

Promise-based acknowledgements

This commit adds some syntactic sugar around acknowledgements:

// without timeoutconstresponse=awaitsocket.emitWithAck("hello","world");// with a specific timeouttry{constresponse=awaitsocket.timeout(1000).emitWithAck("hello","world");}catch(err){// the server did not acknowledge the event in the given delay}

Note: environments thatdo not support Promises will need to add a polyfill in order to use this feature.

Added in47b979d.

Connection state recovery

This feature allows a client to reconnect after a temporary disconnection and restore its ID and receive any packets that was missed during the disconnection gap. It must be enabled on the server side.

A new boolean attribute namedrecovered is added on thesocket object:

socket.on("connect",()=>{console.log(socket.recovered);// whether the recovery was successful});

Added in54d5ee0 (server) andb4e20c5 (client).

Retry mechanism

Two new options are available:

• retries: the maximum number of retries. Above the limit, the packet will be discarded.
• ackTimeout: the default timeout in milliseconds used when waiting for an acknowledgement (not to be mixed up with the already existingtimeout option, which is used by the Manager during the connection)

constsocket=io({retries:3,ackTimeout:10000});// implicit acksocket.emit("my-event");// explicit acksocket.emit("my-event",(err,val)=>{/* ... */});// custom timeout (in that case the ackTimeout is optional)socket.timeout(5000).emit("my-event",(err,val)=>{/* ... */});

In all examples above, "my-event" will be sent up to 4 times (1 + 3), until the server sends an acknowledgement.

Assigning a unique ID to each packet is the duty of the user, in order to allow deduplication on the server side.

Added in655dce9.

Links

• Diff:4.5.4...4.6.0
• Server release:4.6.0
• engine.io-client version:~6.4.0 (diff)
• ws version:~8.11.0 (diff)

Size of the bundles:

This release contains a bump of thesocket.io-parser dependency, in order to fixCVE-2022-2421.

Links:

• Diff:4.5.3...4.5.4
• Server release:4.5.4
• engine.io-client version:~6.2.3
• ws version:~8.2.3

Size of the bundles: