app.js

const express = require('express')
const path = require('path')
const app = express()

const port = process.env.PORT || 4000;

const server = app.listen(port , () => console.log(`server is listening to ${port}`))


const io = require('socket.io')(server)
app.use(express.static(path.join(__dirname,'public')))

let socketsConnected = new Set()

io.on('connection' , onConnected)

function onConnected(socket) {
    socketsConnected.add(socket.id)

    io.emit('clients-total', socketsConnected.size)

    socket.on('disconnect' , () =>{
        socketsConnected.delete(socket.id)
        io.emit('clients-total', socketsConnected.size)
    })

    socket.on('message' ,(data) => {
       socket.broadcast.emit('chat-message', data)
    })

    socket.on('feedback' , (data) => {
        socket.broadcast.emit('feedback' , data)
    })
}