Frequent connection problems when joining a lobby game

[Langbart]

Some users reported via IRC/Forum or the lobby chat to be unable to join each other:

IRC

frankitogamer (Windows, Alpha25, Antivirus software disabled, different wifi)
via IRC 0ad (​18/Aug/21)

23:41 < frankitogamer> The problem is as if it were between us, because
we can join others but not ourselves together, I don't know if I can explain myself

Forum

AJIexander via the Forum (​3/Aug/21)

Me and my friends cannot join each other due to udp port error 20595.
I found the official manual page. Opened ports, turned off the firewall,
antivirus, even tried hamachi, as well as the "STUN" checkbox when
creating the server, nothing helps. Probably - this is due to the fact
that I have a gray ip address? If so, it is worth mentioning in your
official FAQ so that people do not waste time opening ports if it is
useless.

In-Game lobby chat

In the lobby chat this problem can be read at least once a week, because some users have problems connecting to each other. The problem can be easily solved for experienced users, it is enough to point them in the right direction e.g. ​wiki/FAQ, but for beginners it is too troublesome to deal with port forwarding/firewall disabling.

Usually they try, but nobody knows if it really doesn't work or they just did it wrong.

[Langbart]

I am closing this ticket as it does not contain much actionable information. The problem is usually that the user has to add an exception to the local firewall for 0ad and do port forwarding. Done correctly, this usually fixes the problem, it's just tedious to explain it to users each time. Even if they claim to have done so, it could be that the port forwarding was not set up properly or that they still have an active local firewall or antivirus software blocking the connection.

In the past, it was much worse before STUN (​Phab:D364 - 20/Apr/17) was added to the game, which helped solve this issue for many players.

WFG hosting all matches, would be a solution according to elexis:

[12:16:06] elexis the one solution that would fix the issue for good would be WFG hosting all matches
[12:16:13] elexis would also fix rated game escapes