Executing javascript code with node.js

I'm trying to execute a javascript code with node.js, and 开发者_开发问答I get always two errors saying :

.port 1 is not active

.port 2 is not active

This my javascript code :

var http = require('http');
http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello World\n');
}).listen(8124, "127.0.0.1");
console.log('Server running at http://127.0.0.1:8124/');

Any ideas ?

Do you have anything else listening on 8124 already?

netstat -an|grep :8124