Features

Custom transport implementations

Thetransports option now accepts an array of transport implementations:

import{io}from"socket.io-client";import{XHR,WebSocket}from"engine.io-client";constsocket=io({transports:[XHR,WebSocket]});

Here is the list of provided implementations:

Usage:

(1) sincev18.0.0
(2) sincev21.0.0

Added inf4d898e andb11763b.

Test each low-level transports

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

import{io}from"socket.io-client";constsocket=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 (withtransports: ["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 tofalse for now.

Added in579b243.

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 anddiff)
• ws@~8.17.1 (diff)