server_1.js

var fs = require('fs');
var http = require('http');

server_2.js

var fs = require('fs');
var http = require('http');

http.createServer( function(request, response) {
    // do something here
}).listen(8080, '127.0.0.1');

server_3.js

var fs = require('fs');
var http = require('http');

http.createServer( function(request, response) {
    response.writeHead(200, {'Content-Type': 'text/plain'});
    response.end('Hello world!');
}).listen(8080, '127.0.0.1');

server_4.js

var fs = require('fs');
var http = require('http');

http.createServer( function(request, response) {
    fs.readFile('./response.txt', function(err, data) {
        if ( err ) throw err;
        
        response.writeHead(200, {'Content-Type': 'text/plain'});
        response.end(data.toString());
    });
}).listen(8080, '127.0.0.1');