HTTP node.js server on Vercel

[zekageri]

Hi! I have an HTTP node js server hosted on Vercel.com.
I want to use socket io, but it keeps disconnecting.
Vercel automatically assigns some CA to my server, even if it is HTTP only.
Can this be the problem?

Here is my server code:

app.js

const path = require('path');
const express = require('express');
const app = express();
const http = require('http');
const server = http.createServer(app);
const port = 80;

const socketIOHandler = require('./backend/socketIoHandler.js');

app.engine('.html', require('ejs').__express);
app.set('views', path.join(__dirname, 'views'));
app.use(express.static(path.join(__dirname, 'public')));
app.set('view engine', 'html');

socketIOHandler.init(server);

var getIPAddress = function () {
    var interfaces = require('os').networkInterfaces();
    for (var devName in interfaces) {
        var iface = interfaces[devName];

        for (var i = 0; i < iface.length; i++) {
            var alias = iface[i];
            if (alias.family === 'IPv4' && alias.address !== '127.0.0.1' && !alias.internal)
                return alias.address;
        }
    }
    return '0.0.0.0';
}

app.get('/', function (req, res) {
    res.render('hsh/main/index');
});

server.listen(port, () => {
    console.log(`Example app listening on ${getIPAddress()}:${port}`)
});

socketIoHandler.js

const { Server } = require("socket.io");
var io;
var init = function(server){
    io = new Server(server,{
        cors: {
            origin: "/",
            methods: ["GET", "POST"],
            credentials: true
        },
        transports: ['polling','websocket'],
        allowEIO3: true
    });

    io.on('connection', (socket) => {
        console.log('a user connected');
        let count = 0;
        setInterval(()=>{
            socket.emit("hello",`Hello user! Count: ${++count}`);
        },1500);
        
        socket.on('disconnect', () => {
            console.log('user disconnected');
        });

        socket.on("connect_error", (err) => {
            console.log(`connect_error due to ${err.message}`);
        });

    });

}

module.exports = {
    init
}

client side js

var socket = io("/",{transports: ['polling','websocket']});
var message = document.querySelector("#message");
var msgCount = document.querySelector("#msgCount");

var count = 0;
socket.on('hello', function(msg) {
    console.log(msg);
    message.innerHTML = msg;
    msgCount.innerHTML = ++count;
});

socket.on("disconnect",function(){
    console.log("[SocketIO] - Disconnected!");
    message.innerHTML = "[SocketIO] - Disconnected!";
})

console messages

Hello user! Count: 1

WebSocket connection to 'wss://hitec-smart-home-server-git-main-zekageri.vercel.app/socket.io/?EIO=4&transport=websocket&sid=VAYqp8qWdNcnMMloAAAI' failed: Error during WebSocket handshake: Unexpected response code: 400

Hello user! Count: 2
Hello user! Count: 3
Hello user! Count: 4
Hello user! Count: 5

GET https://hitec-smart-home-server-git-main-zekageri.vercel.app/socket.io/?EIO=4&transport=polling&t=OVR4JrN&sid=VAYqp8qWdNcnMMloAAAI 400

[SocketIO] - Disconnected!

and keeps disconnecting and getting messages forever...

[darrachequesne]

Hi! Unfortunately, the Vercel platform is not suited for long-running connections: https://vercel.com/guides/do-vercel-serverless-functions-support-websocket-connections

[zekageri]

Thanks for the answer. That's what i was afraid of. I did read this article tho. Can you recommend a platform where i can host my node js app with socketio?

[darrachequesne]

Any non-serverless platform should work: AWS, GCP, Digital Ocean, ...