Use the global `WebSocket` class for `'websocket'` transport

[kettanaito]

Hi!

I would like to ask if there are any plans on updating SocketIO toolchain to rely on the global WebSocket class that has been available in Node.js since 2023. Presently, SocketIO hard-codes the 'websocket' transport to use ws in Node.js. I would like to have an API that would allow me to use the global WebSocket class instead, similar to how it works in the browser.

Given that SocketIO already works with the browser's WebSocket, and the Node.js (Undici's) implementation of the protocol is faithful, I suppose that supporting this will not require any significant changes to the library. On the other hand, it would help unblock apps and test setups that would benefit greatly from reusing the same global APIs (which is a huge reason the ecosystem shares more and more of them with every passing year).

Thanks!

[darrachequesne]

Hi!

This is already possible since engine.io-client@6.6.0 (socket.io-client@4.8.0):

import { Socket, Fetch, WebSocket } from "engine.io-client";

const socket = new Socket({
  transports: [Fetch, 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.

Release notes: https://github.com/socketio/socket.io/blob/main/packages/engine.io-client/CHANGELOG.md#660-2024-06-21

However, due to backward compatibility, I don't think this can be made the default for now.

[kettanaito]

Hi, @darrachequesne. Oh, I didn't know about that API! This looks great. Please, let me try this out on my test suite and share back my findings.