io.engine undefined?

[SupertigerDev]

Am I being an idiot? why is io.engine undefined?

in the docs, it says i can use io.engine.handleUpgrade, but io.engine seems to be undefined. vs code autosuggestion works tho, just when running the code it says undefined

https://stackblitz.com/edit/node-3y7mbxtu?file=index.js

const { Server } = require('socket.io');

const io = new Server({});

console.log(io.engine); // -> undefined

v4.8.1

[darrachequesne]

Hi!

io.engine is defined once the Socket.IO server is bound to an HTTP server, for example:

import { createServer } from "node:http";
import { Server } from "socket.io";

const httpServer = createServer();
const io = new Server(httpServer);

httpServer.on("upgrade", (req, socket, head) => {
  if (req.url.startsWith("/socket.io/")) {
    io.engine.handleUpgrade(req, socket, head);
  } else {
    socket.destroy();
  }
});

httpServer.listen(3000);

Reference: https://socket.io/docs/v4/server-api/#enginehandleupgraderequest-socket-head

[SupertigerDev]

But if engine is undefined. How will we run that handleUpgrade function?

Edit: oh wait I think I get it. I'll try it out in a second thanks!

Edit2: I wanted to run 2 socket.io servers on a single http server on a different route, I guess that won't be possible

[darrachequesne]

It's possible, but a bit more verbose:

import { createServer } from "node:http";
import { Server } from "socket.io";
import { Server as Engine } from "engine.io";

const httpServer = createServer();

const io = new Server();
const engine = new Engine();
io.bind(engine);

const io2 = new Server();
const engine2 = new Engine();
io2.bind(engine2);

httpServer.on("request", (req, res) => {
  if (res.writableEnded) {
    return; // already handled, nothing to do
  } else if (req.url.startsWith("/first/")) {
    engine.handleRequest(req, res);
  } else if (req.url.startsWith("/second/")) {
    engine2.handleRequest(req, res);
  } else {
    res.writeHead(404);
    res.end();
  }
});

httpServer.on("upgrade", (req, socket, head) => {
  if (req.url.startsWith("/first/")) {
    engine.handleUpgrade(req, socket, head);
  } else if (req.url.startsWith("/second/")) {
    engine2.handleUpgrade(req, socket, head);
  } else {
    socket.destroy();
  }
});

httpServer.listen(3000);