BeaconServer

BeaconServer runs a Subnautica 2 dedicated server on Windows. Players join by IP and port with the Beacon app.

Subnautica 2 has no dedicated server of its own. BeaconServer starts the game headless on a machine with a public IP and port and keeps Beacon's in-game runtime loaded. The release zip bundles that runtime; building this source yourself produces the supervisor only (see Build from source).

What it does

♻️ Crash restarts

Starts Subnautica 2 with the Beacon runtime and starts it again if the game exits. If the game exits within a minute six times in a row, BeaconServer stops and says why in its log instead of looping.

💾 World backups

Takes a snapshot of the world on every game auto-save (when SnapshotsEnabled is on) and on request. A restore takes a snapshot of the running world first, then swaps the save folder in one step, so a failed restore does not leave a half-written world.

📡 Server query

Answers Source A2S query, so monitoring tools can read the server's name, map, player count and player list.

🖥 Server console

Source RCON with help, status, players, ping, save snapshot, save list, say, announce and motd, plus slash commands registered by server mods.

🔐 Admin API

An HTTP API for world backups, save import, health, the player list, the mod list, chat and the live map. Admin routes are signed with a key derived from the RCON password.

🧩 Mods

Loads UE4SS mods through the Beacon runtime, and publishes the server's mod list at GET /api/v1/manifest for the Beacon app to install when a player joins. See docs/MODS.md.

What you need

• Windows 10, 11 or Server, 64-bit
• Subnautica 2 game files on the machine (BeaconServer starts them; it does not ship the game)
• No GPU, and no separate .NET install: release builds are self-contained

Set it up

1. Download Beacon-Server-Windows-x64-v<version>.zip from the latest release. It holds BeaconServer\ (the supervisor and appsettings.json), ue4ss\ and Beacon.dll (the in-game runtime) and tools\ (the injector).
2. Extract it to a stable folder, such as C:\Beacon\.
3. Install the Subnautica 2 game files under the folder set as SnInstallRoot (default C:\Beacon\game): copy your steamapps\common\Subnautica2 folder there, or install with SteamCMD (app 1962700).
4. Edit BeaconServer\appsettings.json (see Settings).
5. Open the ports listed under Ports.
6. Run BeaconServer\BeaconServer.exe.

Players connect with the Beacon app to <host>:<GameplayPort>.

Use the latest release. A run of older release pages carried a zip that held only the supervisor, with no ue4ss\ folder and no Beacon.dll. Players connect to one of those and bounce straight back to the main menu. A complete bundle is around 120 MB and contains ue4ss\Mods\; anything near 50 MB is the broken one. Affected pages say so at the top of their release notes.

Building from this source? You get the supervisor only. The runtime must sit next to the BeaconServer\ folder, or BeaconServer logs an error and the game runs as a plain Subnautica 2 listen server (no password, player list, live map or chat slash commands).

Ports

Keep the ports unique for each server on a machine. The Beacon app works out the query, RCON and admin ports from the gameplay port, so keep these offsets if you want its status, Console and World windows to work.

Port	Protocol	Purpose
GameplayPort	UDP	Subnautica 2 gameplay
GameplayPort + 2	UDP	Source A2S query
GameplayPort + 3	TCP	Source RCON
GameplayPort + 4	TCP	Admin HTTP API and the live map

Settings

BeaconServer reads appsettings.json (next to BeaconServer.exe) under the Beacon section.

Setting	Default	Purpose
InstanceId	default	Stable instance name used in logs, query rules and API responses.
ServerName	empty	Public name shown in the Beacon app and Source query. Empty falls back to the instance id.
SnInstallRoot	C:\Beacon\game	Subnautica 2 install folder. Beacon detects Steam/Epic Win64 and Xbox WinGDK layouts under this root.
SnExecutablePath	empty	Optional direct path to the Subnautica 2 executable, for example an Xbox install's Subnautica2-WinGDK-Shipping.exe.
SnUserDir	C:\Beacon\userdir	User folder of the hosted game; the live save lives under Saved\SaveGames.
SaveDir	C:\Beacon\saves	Snapshot zips and archived saves.
GameplayPort	27015	UDP port players join through.
BeaconControlPort	27016	Reserved (the gameplay+1 slot of the port block).
QueryPort	27017	UDP Source A2S query port.
RconPort	27018	TCP Source RCON port. RCON is off while RconPassword is empty.
HttpPort	27019	TCP admin HTTP API port. 0 turns it off; it also needs RconPassword.
RconPassword	empty	Admin password for RCON; the HTTP API signing key comes from it. Set this before exposing RCON or HTTP.
ServerPassword	empty	Legacy, ignored since v0.3.55. Use BeaconAuthPassword.
BeaconAuthPassword	empty	Join password for remote players. Empty means an open server. Also sets the password flag in Source query.
Admins	[]	SteamID64s, Beacon user ids or display names treated as admin when running mod slash commands from in-game chat. RCON callers are always admin.
MaxPlayers	4	Slot count reported to the app and query clients.
SnapshotsEnabled	true	Snapshot on every game auto-save. When false, only snapshots you ask for run.
MaxUploadBytes	2 GB	Size cap for snapshot uploads and save imports over the HTTP API.
PluginHeartbeatTimeoutSeconds	30	Seconds before BeaconServer treats the game runtime as unresponsive.
Chat:Enabled	true	Filters the mod list only: when false, a beacon-hud entry in Mods is left out of GET /api/v1/manifest, so joining players do not install a chat overlay. It does not add an overlay, and the chat API stays up either way.
Mods	empty	Mod list published at GET /api/v1/manifest: Required, Recommended and Blocked. Re-read on edit; no restart needed.
Map:Enabled	true	Live web map served at /map/ on the admin HTTP port.
Map:Public	false	When true, /api/v1/map/state is readable without auth, so the browser map shows live players to anyone with the URL.

In-game chat is not included in a self-hosted server. Players get a chat window in the game only when the server's Mods list names Beacon's chat overlay (beacon-hud), which the Beacon app then installs when they join. The overlay is not published for self-hosting, so a server set up from this release has no in-game chat window. The RCON and HTTP chat commands (say, announce, motd, /api/v1/chat/*) still run and keep the recent messages, but nothing in the game shows them.

Source query example

BeaconServer answers standard Source A2S queries on QueryPort.

py -m pip install python-a2s
@'
import a2s

address = ("127.0.0.1", 27017)
info = a2s.info(address)
players = a2s.players(address)

print(f"{info.server_name} - {info.player_count}/{info.max_players} on {info.map_name}")
for player in players:
    print(f"{player.name} {player.duration:.0f}s")
'@ | py -

The same port works with tools such as GameDig, LGSM monitors and Discord status bots that support Source query.

RCON

Connect to RconPort with the configured RconPassword.

help
status
players
ping
save snapshot
save list
say <message>
announce <message>
motd [message]

Mod-registered slash commands also run over RCON, with or without the leading /. Restoring a snapshot is not an RCON command; use the Beacon app's World backups window or the HTTP API.

See docs/ADMIN.md for exact command output, the HTTP API signing recipe and the endpoint list.

Rent a server

SurvivalServers.com Subnautica 2 hosting ships the complete Beacon server runtime already installed and handles ports, updates and panel integration.

Build from source

git clone https://github.com/HumanGenome/BeaconServer.git
cd BeaconServer
dotnet build BeaconServer.sln -c Release
dotnet test BeaconServer.sln -c Release --no-build
dotnet publish src/server/BeaconServer/BeaconServer.csproj -c Release -r win-x64 --self-contained true

Published output lands under src/server/BeaconServer/bin/Release/net10.0/win-x64/publish/.

Known issues

"The game was not started via the platform launcher and will be closed."

Subnautica 2 asks the Steam client to confirm the copy of the game it is running. On a headless host that answer often does not come back, and the game closes itself with exit code 0.

Three things have to be true on the server machine:

• The Steam client is running and signed in to an account that owns Subnautica 2. Offline mode is fine.
• Steam is signed in as the same Windows user, in the same session, as the one running BeaconServer. A Steam client in another session is not visible to the game.
• steam_appid.txt containing the single line 1962700 sits next to Subnautica2-Win64-Shipping.exe.

From v0.3.125 BeaconServer writes steam_appid.txt itself on every launch and passes the same id to the game through the environment, so the part left to you is the Steam client. If the game still closes itself, BeaconServer says so in its log and stops relaunching.

Tracked at HumanGenome/Beacon#8.

Game build must match between client and server

After a Subnautica 2 update, players on the new build can fail to join an older server, or join and then get disconnected when they reach something the update changed. Update the server's game files whenever the game updates.

Releases

Each release holds the complete server zip (Beacon-Server-Windows-x64-v<version>.zip) and checksums.txt. The player app is published from HumanGenome/Beacon.

Contributing

Report bugs on Beacon's issue tracker; this repo has issues turned off. Include the BeaconServer version, the Subnautica 2 build, and the relevant lines from logs\beacon-*.log (one JSON object per line, rolled daily). From v0.3.130 that log masks join passwords; check an older log for Password= before posting it. Pull requests are welcome here.

Community note

Beacon is a community project and is not affiliated with or endorsed by the developers of Subnautica 2.

License

MIT. See LICENSE.

Credits

• UE4SS: Unreal Engine scripting and modding framework