running nodejs on amazon ec2

I am trying to run a nodeJS server on an Amazon EC2 instance but I cannot access it in public.

I have read several SO questions about this and also some blogs posts but no solution works for me. This is my server config:

var http = require('http');
http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Simple server\n');
}).listen(4444);
console.log('Server running');

This is the output of iptables -l:

Chain INPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:4444
ACCEPT     tcp  --  anywhere             anywhere             tcp spt:4444

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     tcp  --  anywhere             anywhere             tcp spt:4444

And the port 4444 is also added on the instance's security group.

After the server has started, running curl localhost:4444 echoes the expected "Simple Server". But I am not able to connect to the public DNS / IP address.

Do you know which setting is still missing?