I did some experiment with node earlier

The following code outputs "aaa" to console, and the browser keeps waiting for response, as expected.

```
var http = require("http");

http.createServer(function (req, res) {
  //res.writeHead(200);
  console.log("aaa");
  //res.end("hello");
  //console.log("test111");
  //res.end("bye");
}).listen(5555);

```

Output:

```
aaa

```

But, as soon as I un-comment the first res.end, node writes "aaa" to the console twice on one request!

```
var http = require("http");

http.createServer(function (req, res) {
  res.writeHead(200);
  console.log("aaa");
  res.end("hello");
  //console.log("test111");
  //res.end("bye");
}).listen(5555);

```

Output:

```
aaa
aaa

```

Finally, when I un-comment everything,

```
var http = require("http");

http.createServer(function (req, res) {
  res.writeHead(200);
  console.log("aaa");
  res.end("hello");
  console.log("test111");
  res.end("bye");
}).listen(5555);

```

Output:

```
aaa
test111
aaa
test111

```

Any idea why the console.log statements are executed twice per single request?