index.js

const express = require('express')
const app = express()
const server = require('http').createServer(app)
const cors = require('cors')
app.use(cors())

const PORT = process.env.PORT || 5000

app.get('/', (req, res) => {
    res.send('HELLO SERVER')
})

const io = require('socket.io')(server, {
    cors: {
        origin: '*',
        methods: ["GET", "POST"]
    }
})

io.on('connection', socket => {
    socket.emit('me', socket.id)

    socket.on('disconnect', () => {
        socket.broadcast.emit('callEnded')
    })
    
    socket.on('callUser', ({ userToCall, signalData, from, name }) => {
        io.to(userToCall).emit('callUser', { signal: signalData, from, name })
    })

    socket.on('answerCall', data => {
        io.to(data.to).emit('callAccepted', data.signal)
    })
})

server.listen(PORT, () => {
    console.log('Listening on', PORT)
})