I was just playing cdogs-sdl with a friend over the Internet, which is quite fun!
It was a bit annoying that besides the main listening port (34219), it opens additional random ports that need to be reachable.
So to achieve a connection, I had to lookup the open ports and re-configure my router (firewall/NAT).

It would be nice if cdogs-sdl would choose the open ports from a predictable range (even better if only one port would be sufficient), so that the router needs to be configured only once.