Make request in NodeJs server?

I've created a server http listener : 

var http = require('http');
http.createServer(function (req, res)
{
        res.writeHead(200,
        {
                'Content-Type': 'text/plain'
        });
        res.write('aaa');
        res.end();
}).listen(1337, '127.0.0.1');
console.log('waiting......');

it is working find and do response.

enter image description here

Now , I want - foreach client request - The server to perform another request and append a string "XXX" :

So I wrote : 

var http = require('http');
var options = {
        host: 'www.random.org',
        path: '/integers/?num=1&min=1&max=10&col=1&base=10&format=plain&rnd=new'
};
http.createServer(function (req, res)
{
        res.writeHead(200,
        {
                'Content-Type': 'text/plain'
        });
        res.write('aaa');

        http.request(options, function (r)
        {
                r.on('data', function (chunk)
                {
                        res.write('XXX');
                });
                r.on('end', function ()
                {
                        console.log(str);
                });
                res.end();
        });

        res.end();
}).listen(1337, '127.0.0.1');
console.log('waiting......');

So now foreach request , it should write : aaaXXX ( aaa+XXX)

But it doesnt work . it still egenrated the same output.

What am I dong wrong ?

Try this:

var http = require('http');
var options = {
        host: 'www.random.org',
        path: '/integers/?num=1&min=1&max=10&col=1&base=10&format=plain&rnd=new'
};
http.createServer(function (req, res)
{
        res.writeHead(200,
        {
                'Content-Type': 'text/plain'
        });
        res.write('aaa');

        var httpreq = http.request(options, function (r)
        {
            r.setEncoding('utf8');
            r.on('data', function (chunk)
            {
                res.write(' - '+chunk+' - ');
            });
            r.on('end', function (str)
            {
                res.end();
            });

        });

        httpreq.end();

}).listen(1337, '127.0.0.1');
console.log('waiting......');

Also, worth reading this article on nodejitsu

You're calling res.end() too early... you only want to do thing when EVERYTHING has been written (e.g. when r.on('end') is called).

For something like this, I would highly recommend using the excellent request library (https://github.com/mikeal/request).

This has a wonderful API, for example:

var request = require('request');
request('http://www.google.com', function (error, response, body) {
  if (!error && response.statusCode == 200) {
    console.log(body) // Print the google web page.
  }
})