No firewall. You can't connect to a server listening on 7779 if docker is set to "-p 7779:7777". If you change the port the gameserver is listening on you have to remove the port settings in the template and create them yourself.
Figured it out, the port mapping instructions are wrong but I had to actually think about it. Leave the "game parameter" and config file at 7777 and only change the port values in the screenshot. Query port doesn't matter.