By default, Clonk Rage uses port 11112 TCP and port 11113 UDP for game connections. For directly joining an IP address (without internet server) port 11111 TCP is required incoming on the host.
This site says, port 80 is closed Ports 11112 and 11113 are closed, too, but I think they aren't. My IP adress can't be located and the trace leads from the USA to Austria, the Netherlands, back to Austria and then gets lost in the unknown.