Game servers (lxc) cannot be listed and are unreachable for master servers

[Mister J.]

Hi all,

I successfully run 4 game servers (latest versions of Urban Terror, Unreal Tournament 2004, Xonotic & Warsow) that I can connect to with a client from the LAN and WAN by ip.

Old situation:
LAN (switch with clients) - Gateway server - (LAN) router & WiFi (WAN) - Internet

Since I changed server OS from ClearOS to initially NethServer 7, I am having problems getting listed.
Because someone advised me to solve this problem by simplifying my LAN setup (no double NAT), I changed to Proxmox and now I am running the game servers in Debian 12 based lxc containers (no firewall) with a dedicated OPNsense firewall box and a bridged router.

New situation:
LAN (switch with clients, Proxmox box & Access Point) - (LAN) OPNsense box (WAN) - router (bridged) - Internet

Because I do not have this 'in-game' listing problem with UT2K4, I must assume that it's not something simple like a problem with portforwarding, because those are identical.

But with Urban Terror, Xonotic & Warsow it's only possible to connect from the Internet by ip address and not with the 'in-game'- or online listings.
I already tried every trick in the book that I could find, but nothing works with these 3 games.
https://arena.sh and https://www.urbanterror.info also reports that the servers are unreachable for the master servers.

The problem I have with UT2K4 is that I can't figure out how to add my server to GameTracker.com.
For unknow reasons it reports that one of the following criteria is true:

• Server is not online
• Entered the wrong Query Port
• Server is firewalled

[root@UT2K4 ~]# sudo ss -tuln | grep -E '7777|7778|7787|10777|28902'
udp UNCONN 0 0 192.168.100.142:7777 0.0.0.0:*
udp UNCONN 0 0 192.168.100.142:7778 0.0.0.0:*
udp UNCONN 0 0 192.168.100.142:7787 0.0.0.0:*
udp UNCONN 0 0 192.168.100.142:10777 0.0.0.0:*
udp UNCONN 0 0 192.168.100.142:28902 0.0.0.0:*


[root@UT2K4 ~]# nmap -sU -p 7777,7778,7787,10777,28902 192.168.100.142
Starting Nmap 7.93 ( https://nmap.org ) at 2024-10-20 23:47 UTC
Nmap scan report for UT2K4.<domain>.nl (192.168.100.142)
Host is up.

PORT STATE SERVICE
7777/udp open|filtered cbt
7778/udp open|filtered interwise
7787/udp open|filtered popup-reminders
10777/udp open|filtered unknown
28902/udp open|filtered unknown

Nmap done: 1 IP address (1 host up) scanned in 3.14 seconds


[root@UT2K4 ~]# iptables -L -n
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT 0 -- 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
ACCEPT 17 -- 0.0.0.0/0 192.168.100.142 udp dpt:7777
ACCEPT 17 -- 0.0.0.0/0 192.168.100.142 udp dpt:7778
ACCEPT 17 -- 0.0.0.0/0 192.168.100.142 udp dpt:7787
ACCEPT 17 -- 0.0.0.0/0 192.168.100.142 udp dpt:10777
ACCEPT 17 -- 0.0.0.0/0 192.168.100.142 udp dpt:28902
DROP 0 -- 0.0.0.0/0 0.0.0.0/0

Chain FORWARD (policy ACCEPT)
target prot opt source destination
ACCEPT 17 -- 192.168.100.142 0.0.0.0/0 udp dpt:7777
ACCEPT 17 -- 192.168.100.142 0.0.0.0/0 udp dpt:7787
ACCEPT 17 -- 192.168.100.142 0.0.0.0/0 udp dpt:28902

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

When running these game servers on a ClearOS box in gateway mode (with my router enabled and no OPNsense box) I did not have any of these problems.
Together with a friend of mine who has 35+ years of experience with Proxmox and OPNsense and myself having 20+ years of experience with hosting game servers, we confirmed that all the server- and firewall settings are correct and should work.

Please advice,

Mister J.