server.js

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

const app = express()
const server = http.createServer(app)
const io = new Server(server)

app.use('/', express.static('public'))

io.on('connection', (socket) => {
  socket.on('join', (roomId) => {
    const selectedRoom = io.sockets.adapter.rooms.get(roomId)
    const numberOfClients = selectedRoom ? selectedRoom.size : 0

    if (numberOfClients === 0) {
      console.log(`Creating room ${roomId} and emitting room_created socket event`)
      socket.join(roomId)
      socket.emit('room_created', roomId)
    } else if (numberOfClients === 1) {
      console.log(`Joining room ${roomId} and emitting room_joined socket event`)
      socket.join(roomId)
      socket.emit('room_joined', roomId)
    } else {
      console.log(`Can't join room ${roomId}, emitting full_room socket event`)
      socket.emit('full_room', roomId)
    }
  })

  // These events are emitted to all the sockets connected to the same room except the sender.
  socket.on('start_call', (roomId) => {
    console.log(`Broadcasting start_call event to peers in room ${roomId}`)
    socket.to(roomId).emit('start_call')
  })

  socket.on('webrtc_offer', (event) => {
    console.log(`Broadcasting webrtc_offer event to peers in room ${event.roomId}`)
    socket.to(event.roomId).emit('webrtc_offer', event.sdp)
  })

  socket.on('webrtc_answer', (event) => {
    console.log(`Broadcasting webrtc_answer event to peers in room ${event.roomId}`)
    socket.to(event.roomId).emit('webrtc_answer', event.sdp)
  })

  socket.on('webrtc_ice_candidate', (event) => {
    console.log(`Broadcasting webrtc_ice_candidate event to peers in room ${event.roomId}`)
    socket.to(event.roomId).emit('webrtc_ice_candidate', event)
  })
})

// START THE SERVER =================================================================
const port = process.env.PORT || 3000
server.listen(port, () => {
  console.log(`Express server listening on port ${port}`)
})