🎮 Game Error Codes What it means & how to fix it

Barotrauma Can't Join a Server? Here's the Fix

When Barotrauma can't join — the server list is empty, the invite times out, or you're kicked with a version/mod error — it's usually an EOS/Steam auth issue, a strict NAT/port problem, or a mismatched mod list. Fastest fix: match the host's mod list and game version, log back into Steam, and have the host set the server visible and forward the right port for a dedicated server.

Exact details for Barotrauma

Ports to forward (UDP)
27015 (game) + 27016 (query)
Protocol
UDP — 27015 gameplay, 27016 queries/public listing
Server settings file
serversettings.xml (Barotrauma root, next to Barotrauma.exe)
Common cause of 'cannot connect'
Only 27015 forwarded — 27016 must also be open or the server won't show/authenticate

Error codes

Can't join friend / connection timed out The client never reaches the host's session

Cause: Strict NAT, firewall, or the host isn't listed/visible.

Fix:
  1. Both players must be Steam friends; join via the Steam overlay or Friends tab.
  2. Allow Barotrauma through Windows Firewall (Private + Public).
  3. Host: enable UPnP or forward the server port (default UDP/TCP 27015) for a dedicated server.
  4. Use a wired connection and restart the router to refresh NAT.
Server list empty / can't refresh The lobby browser can't reach the master/EOS list

Cause: EOS or Steam authentication is out of sync.

Fix:
  1. Log out of Steam and back in, then relaunch Barotrauma.
  2. Verify integrity of game files in Steam.
  3. Check the Barotrauma/EOS service status before retrying.
  4. Toggle the lobby filters off and refresh again.
Version / mod mismatch on join Client and host don't share the same build or mod set

Cause: One player updated, is on a beta branch, or has different Workshop mods.

Fix:
  1. Match the host's exact mod list and load order via the Workshop collection.
  2. Update Barotrauma on both machines; opt out of beta branches if needed.
  3. Subscribe to the same mods and enable them in the same order.
  4. Restart both games after syncing mods.

Fixes that work for most Barotrauma errors

  1. Match the host's game version and full mod list/load order.
  2. Both players Steam friends; join via the overlay or Friends tab.
  3. Allow the game through Windows Firewall (Private + Public).
  4. Enable UPnP or forward port 27015 for a dedicated server.
  5. Log out/in of Steam and verify game files if the list is empty.
  6. Use a wired connection and restart the router.

FAQ

Why can't I join my friend's Barotrauma server?

Most often it's NAT/firewall or a mod/version mismatch. Allow the game through Windows Firewall, enable UPnP (or forward port 27015 for a dedicated server), and make sure both players share the exact same game version and mod list/load order.

Why is my Barotrauma server list empty?

That's usually an EOS/Steam auth sync problem. Log out of Steam and back in, verify the game files, check the service status, and clear any lobby filters before refreshing the list again.

What port does a Barotrauma dedicated server use?

By default UDP/TCP 27015. Forward that port on the router (or enable UPnP), keep the host online, and make sure the firewall allows the server executable.

Other games