https://github.com/ismail0234/Subnautica-Below-Zero-Multiplayer
ismail0234/Subnautica-Below-Zero-Multiplayer#383
Connection error If your friend can't connect to your server, or you can't connect to your friend's server, there's no solution other than these 3 steps.
- Steam Offline Mode (don't use Steam in Offline Mode)
- Any VPN program (AvastVPN, NordVPN, etc. / Close your VPN program and try again)
- Antivirus issue (disable your antivirus program and try again)
Important note: Both parties must verify these steps.
[ERROR] [Subnautica.API] Netbird API Exception: System.Exception: The system cannot find the file specified:, IS: False, T: 5000
[21:12:08.390] [INFO] [Subnautica.API] Connecting to server!
[21:12:14.179] [INFO] [Subnautica.API] [Connection] IsReady(0): True, anyError: False, ERR:
[21:12:35.117] [INFO] [Subnautica.Client] Connection Trying (1)
[21:12:35.232] [INFO] [Subnautica.Client] WAIT (0): True
[21:12:35.449] [INFO] [Subnautica.Client] OnPeerDisconnected - Reason: RemoteConnectionClose
[21:12:35.452] [INFO] [Subnautica.Client] ConnectionSignal Detected: Disconnected
[21:13:23.503] [INFO] [Subnautica.API] IsHostConnected: (1)
[21:13:23.803] [INFO] [Subnautica.API] IsHostConnected: (2)
[21:13:24.123] [INFO] [Subnautica.API] IsHostConnected: (3)
[21:13:24.421] [INFO] [Subnautica.API] IsHostConnected: (4)
[21:13:24.721] [INFO] [Subnautica.API] IsHostConnected: (5)
[21:13:25.023] [INFO] [Subnautica.API] IsHostConnected: (6)
[21:13:26.356] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (1)
[21:13:28.402] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (2)
[21:13:29.702] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (3)
[21:13:31.003] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (4)
[21:13:32.303] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (5)
[21:13:34.320] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (6)
[21:13:35.619] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (7)
[21:13:36.919] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (8)
[21:13:38.220] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (9)
[21:13:40.266] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (10)
[21:13:41.567] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (11)
[21:13:42.866] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (12)
[21:13:44.165] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (13)
[21:13:46.202] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (14)
[21:13:47.503] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (15)
[21:13:48.801] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (16)
[21:13:50.100] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (17)
[21:13:52.158] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (18)
[21:13:53.296] [ERROR] [Subnautica.API] Trigger Error Key: JoinServer.Part_5
[21:13:53.458] [INFO] [Subnautica.API] HOST CONNECTION WAITING: (19)
In the error message that pops up when it fails to connect, you get a hit list of "it's your problem" and to fix these things on your machine or your friend's machine.
- Don't run in Steam Offline Mode
- Turn off VPN's
- Turn off Antivirus
And then in the discord there are a few more hints:
- Ensure connectivity to https://subnauticamultiplayer.com
- Figure it out yourself from there. It's not us, it's you. (Issues on github closed without discussion, support tickets about it closed on discord)
Checking in Feb 2026, it looks like this mod does some slick connectivity using NetBird, and a hosted service on
https://lobby.subnauticamultiplayer.com:9443
To create multiple users (via https://zitadel.com/ for auth) and register connections and get them connected.
This style of peer to peer connectivity with STUN/TURN servers to poke through complicated networks is pretty cool.
https://webrtc.link/en/articles/stun-turn-servers-webrtc-nat-traversal/
Note: the netbird exe and the firewall fixer exe's are unpacked/included in the single mod exe.
This use of netbird is supposed to make the cross-platform/launcher connections seamless.
Steam and Epic games create user names and have links to where the exe's are on the machine, but to play a game from their store you need to be logged in to their launcher and then the exe is allowed to open.
To the best of my knowledge, because of the design, you send/receive an invite to connect to someone else's hosted game and connect with a unique username coming from the launcher you are using.
The host instantly connects to their own server, and then the handshake to connect over netbird begins.
Netbird also makes a DNS network adapter with a dns name for it's tunnel it creates.
It looks like it has been a labor of love for a long time for this Turkish developer (and others involved).
Subnautica is awesome. So are the mod developers.