I was using hidden, but having another look at the json file, it seems that I had a 1 in the username and password properties (I don't think I added this from the example file..), removing that (and possibly setting it to LAN) made it work, thanks!

I'm trying to set up a spare machine to run a LAN game that people can join, however it is behind some proxies and firewalls that I don't have control over.

Version is 0.13.20

If I run the game client normally and create a multiplayer game, people can join fine and everything is grand.
If I try to ...