Node.js 为什么express.vhost不是'；不行吗？

我创建了3个节点js服务器。我正在尝试将server2和server3加载到server1中。我正在尝试使用express.vhost，但未能成功。以下是我的代码： 服务器：

服务器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;

服务器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);
});

我把这些文件放在同一个文件夹里。谢谢你的帮助

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);
});