if you are behind a firewall you need to open ports.
permit tcp any any eq 28900 permit udp any any eq 27900 permit udp any any range 23000 23009 permit udp any any eq 22000 permit udp any any range 14567 14570
i dont have a firewall open. a friend said its because of my 'Router'. it makes it possible that 2 people can play through 1 DSL connection. are there other ports for it too?
those are the ports...your router more than likely has a built-in firewall...you will need to "allow" those ports to be forwarded
and how do i "allow" them?
what type of router are you using? there should be a config page, under advanced options look for virtual server or port forwarding...some thing of that nature where you can open ports fort a specific internal IP...if all else fail consult the user manual or FAQ's on the manufacturers site