My application folder structure is something like this.

app/ config/ app.js env.js server.js

Whenever I start my run my app.js file it gives me server started at undefined. Here is the gist of the code.

Gist Codes

server.js    
// Module dependencies.
var http = require('http'),
    app = require('./config/app')();

// Start server
app.listen(app.get('port'), function(){
    console.log('App is Up at '+ app.get('port') + ' as ' + process.env.NODE_ENV);
});

config/app.js
var express  =  require('express'),
    path  =  require('path'),
    ejs  =  require('ejs');

module.exports = function() {
    var app = express();
    var publicDir = path.join(__dirname, '../public');

    // Store all environment variables
    app.set('port', process.env.PORT || 3000);

    // Basic configuration
    app.configure(function() {
        app.use(express.logger('dev'));
        app.use(express.bodyParser());
        app.use(express.methodOverride());
        app.use(app.router);
        app.use(express.static(publicDir));
    });

    // Environment specific configuration
    require('./env')(app);

    return app;
};
config/env.js
var express = require('express'),
    hbsPrecompiler = require('handlebars-precompiler'),
    path = require('path');

module.exports = function(app) {
    // development compile Handlebars and show errors
    app.configure('development', function(){
        app.set('db-uri', process.env.MONGOLAB_URI || 'mongodb://localhost/App');

        hbsPrecompiler.watchDir(
            path.join(__dirname, "../public/templates"),
            path.join(__dirname, "../public/templates/compiled/templates.js"),
            ['handlebars', 'hbs']
        );
        app.use(express.errorHandler());
    });

    app.configure('production', function(){
        app.set('db-uri', process.env.MONGOLAB_URI);
    });
};

node server.js

output

/usr/bin/node app.js
App is Up at 3000 as undefined