So, since connecting without the registry seems to not work, is there a way to make a LAN mode? Where only people on your network can join the server? For example if I wanted to host a contest at a place without any internet connection, and therefore we can have local server serving all people on the same local network.
Even if the registry is down, you can still connect using advanced connection. So there wouldn't be a real problem in LAN, you would just have to know the IP of the server machine on the local network.