TypeError：http.createServer不是函数

Question

我正在尝试在AWS上安装Node，安装完成后，我正在使用http.createServer，这会给我以下错误。

http.createServer(function (req, res) {
     ^

TypeError: http.createServer is not a function
    at Object.<anonymous> (/home/ubuntu/test1/test1.js:4:6)
    at Module._compile (module.js:652:30)
    at Object.Module._extensions..js (module.js:663:10)
    at Module.load (module.js:565:32)
    at tryModuleLoad (module.js:505:12)
    at Function.Module._load (module.js:497:3)
    at Function.Module.runMain (module.js:693:10)
    at startup (bootstrap_node.js:188:16)
    at bootstrap_node.js:609:3

以下是我在test1.js中输入的代码

var http = require('http');
var port = 9000;

http.createServer(function(req, res){
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello there, world\n');
}).listen(port);

console.log("Listening on port " + port);