server.js

// Heroku server.js file

var os = require('os');
var express = require("express");
var bodyParser = require("body-parser");
var socketIO = require('socket.io');
var cors = require('cors');

var app = express();
app.use(cors());

app.use(bodyParser.json());

// Create link to Angular build directory
var distDir = __dirname + "/dist/";
app.use(express.static(distDir));

// Initialize the app.
var server = app.listen(process.env.PORT || 8000, function () {
  var port = server.address().port;
  console.log("App now running on port", port);
});

var io = socketIO(server);
io.sockets.on('connection', function(socket) {

  socket.on('message', function(message) {
    console.log('Client said: ', message);
    // for a real app, would be room-only (not broadcast)
    socket.broadcast.emit('message', message);
  });

  socket.on('create or join', function(room) {
    console.log('Received request to create or join room ' + room);

    var clientsInRoom = io.sockets.adapter.rooms[room];
    var numClients = clientsInRoom ? Object.keys(clientsInRoom.sockets).length : 0;
    console.log('Room ' + room + ' now has ' + numClients + ' client(s)');

    if (numClients === 0) {
      socket.join(room);
      console.log('Client ID ' + socket.id + ' created room ' + room);
      socket.emit('created', room, socket.id);

    } else if (numClients === 1) {
      console.log('Client ID ' + socket.id + ' joined room ' + room);
      io.sockets.in(room).emit('join', room);
      socket.join(room);
      socket.emit('joined', room, socket.id);
      io.sockets.in(room).emit('ready');
    } else { // max two clients
      socket.emit('full', room);
    }
  });

  socket.on('ipaddr', function() {
    var ifaces = os.networkInterfaces();
    for (var dev in ifaces) {
      ifaces[dev].forEach(function(details) {
        if (details.family === 'IPv4' && details.address !== '127.0.0.1') {
          socket.emit('ipaddr', details.address);
        }
      });
    }
  });

});