node.js – 使用response.write节点Js问题

我直接从演示中获取代码,不明白我的问题是什么.
当我卷曲到服务器时,我的标题是正确的.

http/1.1 200 OK
Content-Type: text/plain
Connection: keep-alive
transfer-encoding: chunked


var http = require('http');
    http.createServer(function (req,res) {
      res.writeHead(200,{'Content-Type': 'text/plain'});
      res.write('Hello');
      res.write(':');
      setTimeout(function(){ 
          res.end('World\n')},2000);
    }).listen(1337,"127.0.0.1");
    console.log('Server running at http://127.0.0.1:1337/');

为什么服务器不发送写入数据？