This started since the Game Query and Steam Query port change being hardset. On all of my hardware setups, a HC will not connect to a server on the same hardware, the HC must be remote. We ruled out it being a localclients/headlessclients IP whitelisting issue, as it never connects in the first place, where as a remote headless client, if not whitelisted, connects, but produces a steam ticket issue and is kicked.
All hardware is non virtualized, and uses a /29 IP range or larger (5+ public IPs bound directly).
The HC will bind on 0.0.0.0:2304 UDP and the server will bind to whatever IP -ip= sets it to, and only that IP (which is good), but the HC binding on 0.0.0.0 (all IPs) seems to possibly be part of the problem.
I tried using -ip on the HC to set it to a certain different IP, but then it binds to nothing, only makes an attempt to talk to a steam auth server IP outbound and then closes it (from what I could tell)
If I start the HC before the server, then the server shows up still in the server list, and when trying to join, halts me on the Stratis loading screen, no RPT errors that I can see, server, HC, or client.
Though once I did get this in my client RPT randomly it seems:
16:50:30 c:\w\stable\futura\lib\network\networkserver.cpp ClearNetServer:NOT IMPLEMENTED - briefing!