For people with routers not supporting NAT loopback, it is not possible to join a lobby game from someone hosting from the same network (e.g. another computer, the same computer).
This is annoying because it prevents:
- having a dedicated server at home
- playing with your friends at home via the lobby (which can be easier than via regular MP).
Unfortunately, there is no trivial solution to 2 problems:
- Finding the local IP - I'm using https://stackoverflow.com/a/59025254 but it needs another look
- deciding how to switch local/remote. My approach is to do an external IP query first, then an internal IP query if the first reveals that the IPs are the same. This will be a little slower, but that should be OK in general. We _could_ just return both in one go.