app.js

var express = require('express');
var compression = require('compression');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var path = require('path');
var cors = require('cors');
var http = require('http');

var flockService = require('./lib/services/flockService');
var apiRoutes = require('./routes');
var app = express();

var port = normalizePort(process.env.PORT || '3000');
app.set('port', port);
var server = http.createServer(app);

var io = require('./lib/api/sockets')(server);

app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(compression());

app.use(cors({credentials: true, origin: true}));

app.use('/listener', flockService.events.listener);

app.get('/', (req, res) => {
    res.sendFile(path.join(__dirname, 'index.html'));
});
app.get('/socket.io.js', (req, res) => {
    res.sendFile(path.join(__dirname, 'socket.io.js'));
});

app.use('/api', apiRoutes);

server.on('listening', onListening);
server.on('error', onError);
server.listen(port);

/**
 * Normalize a port into a number, string, or false.
 */

function normalizePort(val) {
  var port = parseInt(val, 10);

  if (isNaN(port)) {
    // named pipe
    return val;
  }

  if (port >= 0) {
    // port number
    return port;
  }

  return false;
}

/**
 * Event listener for HTTP server "error" event.
 */

function onError(error) {
  if (error.syscall !== 'listen') {
    throw error;
  }

  var bind = typeof port === 'string'
    ? 'Pipe ' + port
    : 'Port ' + port;

  // handle specific listen errors with friendly messages
  switch (error.code) {
    case 'EACCES':
      console.error(bind + ' requires elevated privileges');
      process.exit(1);
      break;
    case 'EADDRINUSE':
      console.error(bind + ' is already in use');
      process.exit(1);
      break;
    default:
      throw error;
  }
}

/**
 * Event listener for HTTP server "listening" event.
 */

function onListening() {
  console.log("Magic Happens at port :"  + port);
  var addr = server.address();
  var bind = typeof addr === 'string'
    ? 'pipe ' + addr
    : 'port ' + addr.port;
  console.log('Listening on ' + bind);
}