server.js

const express = require('express');
const http = require('http');
const app = express();
const server = http.createServer(app);
const socket = require('socket.io');
const io = socket(server);

const rooms = {};

const PORT = process.env.PORT || 8000;

app.get('/user', function (req, res) {
  console.log('/user request called');
  res.send('Welcome to GeeksforGeeks');
});

io.on('connection', socket => {
  /*
        If a peer is initiator, he will create a new room
        otherwise if peer is receiver he will join the room
    */
  socket.on('join room', roomID => {
    if (rooms[roomID]) {
      // Receiving peer joins the room
      rooms[roomID].push(socket.id);
    } else {
      // Initiating peer create a new room
      rooms[roomID] = [socket.id];
    }

    /*
            If both initiating and receiving peer joins the room,
            we will get the other user details.

            For initiating peer it would be receiving peer and vice versa.
        */
    const otherUser = rooms[roomID].find(id => id !== socket.id);
    if (otherUser) {
      socket.emit('other user', otherUser);
      socket.to(otherUser).emit('user joined', socket.id);
    }
  });

  /*
        The initiating peer offers a connection
    */
  socket.on('offer', payload => {
    io.to(payload.target).emit('offer', payload);
  });

  /*
        The receiving peer answers (accepts) the offer
    */
  socket.on('answer', payload => {
    io.to(payload.target).emit('answer', payload);
  });

  socket.on('ice-candidate', incoming => {
    io.to(incoming.target).emit('ice-candidate', incoming.candidate);
  });
});

server.listen(PORT, e => {
  console.log('Server is up and running on Port 8000');
});