simpleServer.js

// Require the http core module
var http = require('http');

// Create a server and provide a function (callback) that
// gets called for every request
http.createServer(function (req, res) {
    // Speccify a content type
    res.writeHead(200, {'Content-Type': 'text/plain'});
    
    // Write into the response object sent to the client
    res.write('Hello World!');
    
    // End the request
    res.end();
}).listen(4242); // Tell the HTTP server on which port it should listen