How to Host a Sunkenland Dedicated Server

Sunkenland is a small-group survival game built around a flooded post-apocalypse, capped at 15 players per server. If you want a world that keeps ticking when you log off — so your raft city survives, raids actually mean something, and friends can drop in across time zones — you need a dedicated server. This guide covers two ways to get there: standing one up yourself on a spare Windows box, or running it on LOW.MS so you don't have to babysit the machine.

The setup is quirky compared to most survival games. There's no router port forwarding to deal with, the server has no RCON, and players join via a ServerID string rather than an IP. Once you understand those three things, the rest is straightforward.

What You Need to Know Before You Start

Sunkenland uses Steam Datagram Relay for client-server connections. That means there's nothing to port-forward on your router, no firewall rules to write for inbound traffic, and no public IP to share with players — Steam's relay network handles the join. The server process itself does still bind to local UDP ports for its own socket (you can override them with -port and -queryport if you need to run multiple instances on the same box, otherwise the defaults are fine). Players just need to be on the same region as the server.

A few hard rules worth knowing up front:

• You need to own Sunkenland on Steam to download the dedicated server binaries via SteamCMD — the server lives behind the same Steam login.
• The 15-player cap is a hard limit. Not a soft suggestion, not "officially supported but you can push it". Fifteen.
• Players join with a ServerID, a GUID printed to the server console at startup. That ServerID changes every time the server restarts, so don't bookmark it.
• There is no RCON. Admin and ban management is done by editing two text files inside the world folder.
• Server is Windows-only. Vector3 Studio has not shipped a Linux build.

Path 1: Self-Hosting on Your Own Windows Machine

Install SteamCMD somewhere sensible and run:

steamcmd +force_install_dir "Your_Installation_Directory" +login "Your_User_Name" "Your_Password" +app_update 2667530 validate +quit

The Sunkenland dedicated server app ID is 2667530. Use your own Steam credentials — Steam Guard will prompt you the first time. Once it finishes, you'll have a start_headless_server.bat in the install directory that you'll edit shortly.

Before you can actually launch, you need a world to point the server at. That's the next section.

Path 2: Hosting with LOW.MS

If you'd rather not keep a Windows machine running 24/7, order a Sunkenland server and pick a region close to your group. The server gets provisioned automatically — including its local game and query ports — and you'll log into control.low.ms to manage it.

You'll spend most of your time in three sidebar items:

• File Manager (or SFTP on port 8822) for uploading your prepared world folder.
• Commandline Manager for setting startup arguments — region, password, world GUID, player cap.
• Web Console for watching the startup log and grabbing the ServerID each time the server boots.

Steam Update, Cloud Backup, and Cloud Restore handle the boring parts.

Preparing Your World

This is the step that catches people out: you cannot create a fresh world from the dedicated server. The server only loads existing worlds. You need to launch Sunkenland on your own PC, start a singleplayer game, configure the world the way you want it, save, and quit.

Your world will be saved at:

C:\Users\<You>\AppData\LocalLow\Vector3 Studio\Sunkenland\Worlds\<WorldName>~<GUID>\

The folder name is two parts joined by a tilde — the world name you typed, then a GUID. Copy the entire folder. If you're self-hosting, drop it into the equivalent path on the server machine. If you're on LOW.MS, upload it via File Manager or SFTP into the corresponding Worlds directory. The full walkthrough for that move — exact paths, File Manager, SFTP — is in our Sunkenland save location guide.

Note the GUID — the part after the ~. You'll need it in the next step.

Pointing the Server at Your World

Open start_headless_server.bat (self-hosting) or the Commandline Manager (LOW.MS) and build your argument list. The two flags you must never remove are:

-nographics -batchmode

Strip those and the server will try to spin up a graphical Unity process and fall over. Everything else is layered on top:

• -worldGuid <GUID> — the GUID from your world folder. Technically optional in the manual, in practice required if you want to load a specific world.
• -region <code> — one of asia, cn, jp, eu, sa, kr, us, usw. Pick the one closest to most of your players.
• -maxPlayerCapacity <3-15> — defaults to 3. Set it to 15 if you want the full cap.
• -password <pass> — up to 8 ASCII characters. More on that in the gotchas.
• -makeSessionInvisible — hides the server from the public browser. Useful for private groups.
• -port <n> — local UDP game port the server binds to. The default works fine; only set this if you need to run multiple instances on one machine. On LOW.MS this is allocated for you.
• -queryport <n> — local UDP query port (defaults to game port + 1). Same story — leave it alone unless you're stacking instances.
• -logFile <path> — handy for self-hosting if you want logs somewhere specific.

A typical line ends up looking like:

Sunkenland.exe -nographics -batchmode -worldGuid 4f8a... -region eu -maxPlayerCapacity 15 -password reefclub

Admin and Ban Lists

Inside your world folder (the same one you uploaded), you can create two text files:

• AdminSteamIDs.txt — one Steam64 ID per line. Anyone listed can kick and ban from the in-game menu.
• BanSteamIDs.txt — one Steam64 ID per line. Anyone listed gets disconnected on join.

That's the whole admin system. No commands, no RCON, no web panel toggles. One ID per line, no commas, no comments, nothing else in the file. If you add or remove someone, restart the server to pick up the change.

Joining the Server

When the server finishes booting, the console prints a line like:

Server Start Complete, Ready for Clients to Join. ServerID is '<GUID>'.

That GUID is the ServerID. Send it to your players along with the region you set. In Sunkenland's multiplayer menu they switch to the matching region, paste the ServerID, enter the password if you set one, and they're in. No IP, no port — just ServerID and region.

The catch: the ServerID regenerates on every restart. Don't put it in a Discord pin and forget about it. If you restart the server (for an update, a config change, anything), grab the new ServerID from the Web Console and reshare.

Updates

When Vector3 Studio ships a patch, run the same SteamCMD command without the validate flag:

steamcmd +force_install_dir "Your_Installation_Directory" +login "Your_User_Name" "Your_Password" +app_update 2667530 +quit

On LOW.MS, click Steam Update in the sidebar — same effect, no SteamCMD required. Update both the server and every client to the same version before anyone tries to join, otherwise the connection will silently fail.

Common Gotchas

A few things trip people up consistently:

• Region mismatch is the number one reason joins fail. If your server is on eu and a player's Sunkenland client is set to us, they won't see the server and the ServerID won't connect. Always tell people the region.
• Passwords cap at 8 ASCII characters. Anything longer or anything with non-ASCII characters (accents, emoji, smart quotes) will fail password verification. Keep it short and plain.
• 15 players means 15. The game won't go above 15 — anything higher gets ignored or capped, and there's no clean error to tell you which.
• The ServerID changes on every restart. Treat it as ephemeral. The world data persists; the join string does not.
• No world means no server. If you launch without -worldGuid pointing at an actual prepared world folder, the server will not spin up a fresh one for you.

Get those right and a Sunkenland server is one of the lower-maintenance survival games to run — no router port forwarding to debug, no RCON wrapper to configure, just a world folder and a handful of flags.