Node.js

// Setup
var http = require('http');	// require http module
var port = 80; 			// http port
var host = '127.0.0.1' 		// localhost

// This function will be called when a request arrives from a client
function onRequest(request, response) {
  response.writeHead(200, {'Content-Type': 'text/plain'}); // headers
  response.end('Hello World');				   // end response
}

// Create the http server which will pass requests to `onRequest`
var server = http.createServer(onRequest)
server.listen(port, host);

// Log that the server is running
console.log('Server running at http://127.0.0.1:1337/');