Killing Floor 2 Server Troubleshooting

KF2 Server Troubleshooting

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Server Not Appearing in the Steam Server Browser

The most common issue — players can't find your server.

Check 1 — Firewall ports

Make sure UDP 7777 (game) and UDP 27015 (Steam query) are open:

sudo ufw status

Both should appear in the ALLOW list. If not:

sudo ufw allow 7777/udp
sudo ufw allow 27015/udp
sudo ufw reload

Check 2 — Cloud/VPS security group

If you're on AWS, DigitalOcean, Vultr, Hetzner, etc., there may be a separate firewall in the provider's control panel (security groups, cloud firewalls). The OS firewall and the cloud firewall are independent — both must allow the ports.

Check 3 — Server startup lag

The Steam server browser can take 5–15 minutes to index a newly started server. Try connecting directly by IP first to confirm the server is running.

Direct connection test:

1. In KF2, go to Multiplayer → Server Browser
2. Click Add Server
3. Enter YOUR_IP:7777

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Players Can Connect but Latency is Very High

• Confirm the server is in a datacenter geographically close to your players
• Check CPU usage with top — KF2 is single-threaded for game logic; high CPU on a single core will cause lag
• Reduce MaxPlayers if the server is overloaded (above 6 is not well supported)

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WebAdmin Not Loading

Check 1 — Is it enabled?

In KFGame/Config/KFWeb.ini:

[IpDrv.WebServer]
bEnabled=true
ListenPort=8080

If bEnabled is false or the file doesn't exist, WebAdmin won't start.

Check 2 — Is port 8080 open?

sudo ufw allow 8080/tcp

Check 3 — Is the server actually running?

sudo systemctl status kf2server

If it's not running, check the logs:

journalctl -u kf2server -n 50

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Map Won't Load / Server Crashes on Map Change

Case sensitivity: On Linux, KF-bioticslab is not the same as KF-BioticsLab. All map names in GameMapCycles must exactly match the filename.

Missing custom map: If you added a custom map to the cycle but the file isn't in KFGame/Published/BrewedPC/Maps/, the server will fail to load it. Verify the file exists:

ls /home/steam/kf2server/KFGame/Published/BrewedPC/Maps/

Corrupt map file: Re-download the .kfm file. Check the file size matches the source.

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Server Crashes on Startup

Check the log at KFGame/Logs/Launch.log:

tail -100 /home/steam/kf2server/KFGame/Logs/Launch.log

Common causes:

• A mutator package that doesn't exist or has the wrong path
• A missing or malformed LinuxServer-KFGame.ini
• Corrupt server files — run app_update 232130 validate via SteamCMD

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Config Changes Not Taking Effect

KF2 writes config files on clean shutdown. If you edit a .ini file while the server is running, your changes may be overwritten on the next clean stop.

Correct workflow:

1. Stop the server (sudo systemctl stop kf2server)
2. Edit the config file
3. Start the server (sudo systemctl start kf2server)

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"Authentication Failed" or Players Disconnecting

• Confirm the server has a stable internet connection
• Check that UDP 20560 is open (Steam client communications)
• Verify that your server IP hasn't changed — some VPS providers assign ephemeral IPs on restart