"ALmost all wireless devices have internal NAT firewalls. What you need to do is enable UPnP on the device if it supports UPnP, else forward a port. "

I don't have any wireless devices .. Cause the provider's main antena is placed at the roof of mu building... so I didn't have to by any additional devices but only a cable and to connect directly to the antena.

Others have to by a small antena and to make a real wirelles antena... Me, I am directly connected to server by cable.

SO do I have to do things with UPnP also? Or just forward a port?

"Also you should configure your XP firewall or any other firewall you're using. "

No... My Win XP FW is off... And the one I used is Kaspersky... But I also turned it off. So I have no firewalls.