Issue not resolved here. I keep getting "nat punch failed" .
Well NAT hole punching for UDP works on ~90% of the routers, but may fail on routers that use port-restricted NAT; AFAIK in that case at least one player must set up port forwarding on the router otherwise the NAT tables on the router will discard the DC traffic.
You should either ask Larian about the port numbers or run "netstat -a -b -n" while playing with other players connected and set up port forwarding for all entries where the state is "LISTENING" and has the DC exe filename under it.
I tried that and I can find dcapp.exe using a udp connection, but nowhere in "LISTENING" . So I tried forwarding that particular port under dcapp.exe (you know, setting up static ip for my gaming pc, instruct router to forward that port (e.g. :49988)), nothing helps!