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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.

Dependencies

• engine.io@~6.6.0 (no change)
• ws@~8.17.1 (no change)

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Bug Fixes

• bundle: do not mangle the "_placeholder" attribute (ca9e994)

Dependencies

• engine.io-client@~6.6.1 (no change)
• ws@~8.17.1 (no change)

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Bug Fixes

• types: remove ws type from .d.ts file (175a2c5)
• prevent infinite loop with Node.js built-in WebSocket (4865f2e)

Dependencies

• ws@~8.17.1 (no change)

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This release contains a bump of the cookie dependency.

See also: GHSA-pxg6-pf52-xh8x

Dependencies

• ws@~8.17.1 (no change)

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Bug Fixes

• allow to join a room in a middleware (uws) (b04fa64)
• correctly await async close on adapters (#4971) (e347a3c)
• expose type of default engine (132d05f)

Dependencies

• engine.io@~6.6.0 (diff and diff)
• ws@~8.17.1 (diff)

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Features

Custom transport implementations

The transports option now accepts an array of transport implementations:

import { io } from "socket.io-client";
import { XHR, WebSocket } from "engine.io-client";

const socket = io({
  transports: [XHR, WebSocket]
});

Here is the list of provided implementations:

Transport	Description
Fetch	HTTP long-polling based on the built-in fetch() method.
NodeXHR	HTTP long-polling based on the XMLHttpRequest object provided by the xmlhttprequest-ssl package.
XHR	HTTP long-polling based on the built-in XMLHttpRequest object.
NodeWebSocket	WebSocket transport based on the WebSocket object provided by the ws package.
WebSocket	WebSocket transport based on the built-in WebSocket object.
WebTransport	WebTransport transport based on the built-in WebTransport object.

Usage:

Transport	browser	Node.js	Deno	Bun
Fetch	✅	✅ (1)	✅	✅
NodeXHR		✅	✅	✅
XHR	✅
NodeWebSocket		✅	✅	✅
WebSocket	✅	✅ (2)	✅	✅
WebTransport	✅	✅

(1) since v18.0.0
(2) since v21.0.0

Added in f4d898e and b11763b.

Test each low-level transports

When setting the tryAllTransports option to true, if the first transport (usually, HTTP long-polling) fails, then the other transports will be tested too:

import { io } from "socket.io-client";

const socket = io({
  tryAllTransports: true
});

This feature is useful in two cases:

• when HTTP long-polling is disabled on the server, or if CORS fails
• when WebSocket is tested first (with transports: ["websocket", "polling"])

The only potential downside is that the connection attempt could take more time in case of failure, as there have been reports of WebSocket connection errors taking several seconds before being detected (that's one reason for using HTTP long-polling first). That's why the option defaults to false for now.

Added in 579b243.

Bug Fixes

• accept string | undefined as init argument (bis) (60c757f)
• allow to manually stop the reconnection loop (13c6d2e)
• close the engine upon decoding exception (04c8dd9)
• do not send a packet on an expired connection (#5134) (8adcfbf)

Dependencies

• engine.io-client@~6.6.1 (diff and diff)
• ws@~8.17.1 (diff)

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Bug Fixes

• discard all pending packets when the server is closed (923a12e)
• uws: prevent the client from upgrading twice (d5095fe)

Dependencies

• ws@~8.17.1 (no change)

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Bug Fixes

• move 'offline' event listener at the top (8a2f5a3)
• only remove the event listener if it exists (9b3c9ab)
• do not send a packet on an expired connection (#5134) (8adcfbf)

Performance Improvements

• do not reset the heartbeat timer on each packet (7a23dde)

Dependencies

• ws@~8.17.1 (no change)

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Bug Fixes

• do not expose the TransformStream type (f9cb983)

2.5.1

Bug Fixes

• add a noop handler for the error event (d30630b)

Links:

• Diff: 2.5.0...2.5.1
• Client release: -
• engine.io version: ~3.6.0 (no change)
• ws version: ~7.5.10