Node.js express模块 http服务

var express = require('express');
var app = express();

app.get('/', function(req, res){
  res.send('hello world');
});

var server = app.listen(3000,'localhost', function(){

    var host = server.address().address;
    var port = server.address().port;
    console.log("App is running at http://%s:%s", host, port);
})