Why express.vhost isn't working? - node.js

Question

I create 3 node js servers.I'm trying to load server2 and server3 into server1.I'm trying with express.vhost but i can't succed.Here is my code:
server:
var application_root = __dirname,
express = require( 'express' ),
vhost = require( 'vhost' );
function createVirtualHost(domainName, dirPath) {
return vhost(domainName, express.static( dirPath ));
}
//Create server
var app = express();
//Create the virtual hosts
var host1 = createVirtualHost("http://localhost:8001", "/");
var host2 = createVirtualHost("http://localhost:8002", "/");
//Use the virtual hosts
app.use(host1);
//app.use(host2);
//Start server
var port = 80;
app.listen( port, function() {
console.log( 'Express server listening on port %d in %s mode', port, app.settings.env );
});
server 1 :
var http = require('http');
//Lets define a port we want to listen to
const PORT=8001;
//We need a function which handles requests and send response
function handleRequest(request, response){
response.end('It Works!! Path Hit: ' + request.url);
}
//Create a server
var server = http.createServer(handleRequest);
//Lets start our server
server.listen(PORT, function(){
//Callback triggered when server is successfully listening. Hurray!
console.log("Server listening on: http://localhost:%s", PORT);
});
module.exports=server;
server 3:
var http = require('http');
//Lets define a port we want to listen to
const PORT=8002;
//We need a function which handles requests and send response
function handleRequest(request, response){
response.end('It Works!! Path Hit: ' + request.url);
}
//Create a server
var server = http.createServer(handleRequest);
//Lets start our server
server.listen(PORT, function(){
//Callback triggered when server is successfully listening. Hurray!
console.log("Server listening on: http://localhost:%s", PORT);
});
I have these files in the same folder.Thanks for any help!