Nodejs application with express-generator, and trying to add primus websocket

we're currently trying to build a nodejs app that works with express-generator. I'm currently trying to add the Primus websocket into my application. The problem is that if I don't add app.listen(port) into my app.js file, my app won't show on localhost:3000, even though it's included in the bin/www-file. If I add app.listen(port), my app can't seem to find the primus library although I installed it into my dependencies. I don't know if the problem that my app can't find the primus library is related to the fact that I whether or not add app.listen(port).

My app.js file [

var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var flash = require('connect-flash');
var cookieParser = require('cookie-parser');
var session = require('express-session');
var passport = require('passport');
var Strategy = require('passport-facebook').Strategy;
var bodyParser = require('body-parser');
var mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/facebookusers');
var http = require("http");
var Primus = require("primus");

var options = {
    transformer: "engine.io"
}

var facebook = require('./routes/facebook');
var users = require('./routes/users');
var profile = require('./routes/profile');
var login = require('./routes/login');
var admin = require('./routes/admin');
var vote_now = require('./routes/vote_now');
var vote_result = require('./routes/vote_result');
var groups = require('./routes/groups');
var endvoting = require('./routes/endvoting');
var roles = require('./routes/roles');

var app = express();

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'pug');

// uncomment after placing your favicon in /public
//app.use(favicon(path.join(__dirname, 'public', 'favicon.ico')));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));
app.use(require('morgan')('combined'));
app.use(session({ secret: 'marioWim' }));
app.use(passport.initialize());
app.use(passport.session());
app.use(flash());

app.use('/users', users);
app.use('/profile/', profile);
app.use('/login', login);
app.use('/admin/', admin);
app.use('/vote_now', vote_now);
app.use('/vote_result', vote_result);
app.use('/auth/facebook', facebook);
app.use('/groups', groups);
app.use('/endvoting', endvoting);
app.use('/roles',roles);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

// error handler
app.use(function(err, req, res, next) {
  // set locals, only providing error in development
  res.locals.message = err.message;
  res.locals.error = req.app.get('env') === 'development' ? err : {};
  // render the error page
  res.status(err.status || 500);
  res.render('error');
});

app.listen(3000);

module.exports = app;

my package.json file

{
  "name": "demo-or-die",
  "version": "0.0.0",
  "private": true,
  "scripts": {
    "start": "node ./bin/www"
  },
  "dependencies": {
    "body-parser": "^1.17.1",
    "connect-ensure-login": "^0.1.1",
    "connect-flash": "^0.1.1",
    "cookie-parser": "^1.4.3",
    "debug": "~2.6.3",
    "engine.io": "^3.1.0",
    "express": "~4.15.2",
    "express-session": "^1.15.2",
    "flash": "^1.1.0",
    "jade": "~1.11.0",
    "mongoose": "^4.9.6",
    "morgan": "^1.8.1",
    "named-routes": "^2.0.6",
    "passport": "^0.3.2",
    "passport-facebook": "^2.1.1",
    "primus": "^7.0.1",
    "prompt": "^1.0.0",
    "pug": "^2.0.0-beta.12",
    "serve-favicon": "~2.4.2"
  },
  "devDependencies": {
    "gulp": "^3.9.1",
    "gulp-changed": "^3.0.0",
    "gulp-imagemin": "^3.2.0",
    "gulp-nodemon": "^2.2.1",
    "gulp-sass": "^3.1.0"
  }
}

my bin/www

#!/usr/bin/env node

/**
 * Module dependencies.
 */

var app = require('../app');
var debug = require('debug')('demo-or-die:server');
var http = require('http');

/**
 * Get port from environment and store in Express.
 */

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

/**
 * Create HTTP server.
 */

var server = http.createServer(app);


/**
 * Listen on provided port, on all network interfaces.
 */

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

/**
 * 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() {
  var addr = server.address();
  var bind = typeof addr === 'string'
    ? 'pipe ' + addr
    : 'port ' + addr.port;
  debug('Listening on ' + bind);
}

via Mario Samison