How to call child process in nodejs

[kis...@tbionline.in]

I am learning Nodejs. I want to run two scripts(one is login and another is chat) in URL. When i run npm start command then my login page(app.js) is opened up and when i run node index.js command then my chat application work. I want my chat application to be work after login. So where i should specify my chat index.js so it will work.

My app.js is here

var http = require('http');
var express = require('express');
var session = require('express-session');
var bodyParser = require('body-parser');
var errorHandler = require('errorhandler');
var cookieParser = require('cookie-parser');
var MongoStore = require('connect-mongo')(session);
var routes = require('./routes/index');
var users = require('./routes/users');
var app = express();

app.set('port', process.env.PORT || 3000);
app.set('views', __dirname + '/app/server/views');
app.set('view engine', 'jade');
app.use(cookieParser());
app.use(session({
secret: 'faeb4453e5d14fe6f6d04637f78077c76c73d1b4',
proxy: true,
resave: true,
saveUninitialized: true,
store: new MongoStore({ host: 'localhost', port: 27017, db: 'nodechat'})
 })
);
  app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
app.use(require('stylus').middleware({ src: __dirname + '/app/public'    }));
app.use(express.static(__dirname + '/app/public'));

require('./app/server/routes')(app);

if (app.get('env') == 'development') app.use(errorHandler());

http.createServer(app).listen(app.get('port'), function(){
console.log('Express server listening on port ' + app.get('port'));
});