Space Engineers server: config and PCU

A Space Engineers dedicated server is a free Windows program (Steam app 298740, anonymous download) that loads one world and keeps it running with nobody online. Its settings live in SpaceEngineers-Dedicated.cfg plus the world's own Sandbox_config.sbc, it listens on UDP 27016 by default, and the number that decides whether it stays playable is not RAM or player count but sim speed - the ratio of simulated time to real time, which should sit at 1.0. Everything that drags sim speed down is physics: grids, subgrids, collisions and scripts. PCU limits exist to stop players building more physics than the CPU can afford. Get the limits right before the first base goes up and the server will be pleasant for months; set them afterwards and you are deleting somebody's ship.

How Space Engineers hosting works#

There are three ways to run a multiplayer world, and they are not interchangeable:

• Lobby (hosted from the game): one player's PC runs the world and plays at the same time. The world exists only while they are online, and their frame rate competes with the simulation.
• Dedicated server (Keen's own): SpaceEngineersDedicated.exe from app 298740. It has a configuration GUI on Windows and can run headless as a console process or a Windows service.
• Torch: a community wrapper around the same dedicated server that adds a plugin system, a better admin interface and the Essentials plugin most public servers rely on. It is not an official product and it lags behind game updates by hours or days.

The server is Windows-only. On Linux it runs under Wine, and community container images exist that do exactly that, but Keen does not support it and a game update occasionally breaks the Wine setup before anybody fixes it. If you are choosing a machine for a long-lived server, a Windows VDS is the zero-surprise option; Linux plus Wine works and is cheaper, provided you accept that you are the support desk. Choosing between a VDS and a game panel goes through that trade in general.

Space Engineers 2 is a separate game with its own server story, still moving during early access. Nothing below applies to it unless stated.

Requirements: CPU first, then memory#

Space Engineers is the purest example of a game where CPU matters more than RAM. Physics runs largely on one thread, so clock speed sets the ceiling. Memory grows with the number of grids loaded around players and with mods.

• Disk: the server installs to roughly 10 GB. A world folder starts small and grows into the hundreds of megabytes as players build; with mods add the mod cache. NVMe shortens the save hitch noticeably.
• Planets cost memory: every loaded planet keeps voxel data around players. A world with the full solar system preset uses more than a single-planet start or pure empty space.
• Players cost through what they build, not through being online. Ten people mining asteroids are cheap; three people with rotor-based mining rigs and a printer wall are not.

Installing and first start#

On Windows with SteamCMD:

$ steamcmd +force_install_dir C:\se-server +login anonymous +app_update 298740 validate +quit

SteamCMD explained covers what validate does and why anonymous login works for this app. The install contains DedicatedServer64\SpaceEngineersDedicated.exe. Run it without arguments and you get Keen's configurator: pick a world template or an existing save, fill in the name and limits, then either start the server in that window or save the configuration.

For a headless server, start it with -console:

$ SpaceEngineersDedicated.exe -console -path "C:\se-server\instance"

The three arguments worth knowing:

• -console runs it as a console process with no GUI.
• -path points it at an instance folder, which holds SpaceEngineers-Dedicated.cfg, the Saves folder and the logs. Without it, the default is %AppData%\SpaceEngineersDedicated.
• -ignorelastsession loads the world named in the config instead of the last session the server ran.

The first start downloads nothing extra for a vanilla world, but with mods listed it fetches them from the Steam Workshop before loading, which can take minutes. Watch the log for the line saying the game is ready and the server has been registered with Steam.

SpaceEngineers-Dedicated.cfg: the settings that matter#

The config is XML. Server-level settings sit at the top; world rules sit inside <SessionSettings>. A trimmed example:

<MyConfigDedicated>  <SessionSettings>    <GameMode>Survival</GameMode>    <MaxPlayers>12</MaxPlayers>    <AutoSaveInMinutes>5</AutoSaveInMinutes>    <ViewDistance>15000</ViewDistance>    <SyncDistance>3000</SyncDistance>    <EnableIngameScripts>true</EnableIngameScripts>    <BlockLimitsEnabled>PER_PLAYER</BlockLimitsEnabled>    <TotalPCU>200000</TotalPCU>    <TrashRemovalEnabled>true</TrashRemovalEnabled>    <InventorySizeMultiplier>3</InventorySizeMultiplier>    <AssemblerSpeedMultiplier>3</AssemblerSpeedMultiplier>    <RefinerySpeedMultiplier>3</RefinerySpeedMultiplier>  </SessionSettings>  <LoadWorld>C:\se-server\instance\Saves\Frontier\Sandbox.sbc</LoadWorld>  <IP>0.0.0.0</IP>  <ServerPort>27016</ServerPort>  <SteamPort>8766</SteamPort>  <ServerName>Frontier Engineering</ServerName>  <WorldName>Frontier</WorldName>  <PauseGameWhenEmpty>false</PauseGameWhenEmpty>  <Administrators>    <unsignedLong>76561198012345678</unsignedLong>  </Administrators></MyConfigDedicated>

What each important setting does:

The thing that confuses everyone: an existing world carries its own copy of the session settings in Saves\<World>\Sandbox_config.sbc. The dedicated config's SessionSettings are what a new world is created with; once the world exists, what the world file says is what you get, and some configurators write to both. The reliable method is to stop the server, change the value in Sandbox_config.sbc and in the dedicated config so they agree, and start it again. Editing either while the server runs is pointless - it rewrites them on save.

PCU and block limits#

PCU stands for Performance Cost Unit. Every block has a PCU value reflecting what it costs the server: armour blocks are cheap, functional blocks cost more, and anything with moving physics or a script costs the most. A grid's PCU is the sum of its blocks; a player's or faction's PCU is the sum of everything they own.

BlockLimitsEnabled decides how TotalPCU is enforced:

• `NONE`: no limit. Fine for two friends in creative, dangerous anywhere else.
• `GLOBALLY`: one shared pool for the world. Simple, but the first heavy builder eats everyone's allowance.
• `PER_PLAYER`: the total is divided among players. Predictable, and the usual choice for small private servers.
• `PER_FACTION`: the total is divided among factions, which encourages people to group up. Many public servers use this, often with a cap on faction size.

Defaults have changed between versions and differ by world preset, so open your world's Sandbox_config.sbc and read the actual values rather than trusting a guide. Alongside PCU there are MaxGridSize (blocks per grid) and MaxBlocksPerPlayer, and per-block-type limits that restrict counts of specific expensive blocks such as drills or projectors. A useful starting point for a small group is per-player PCU somewhere in the tens of thousands, a grid size cap that allows a real capital ship, and a limit on projectors.

What PCU does not capture well is behaviour. A 3,000-PCU rotor-and-piston contraption that collides with itself every tick can cost more than a 30,000-PCU static station. So limits are necessary but not sufficient - you also need cleanup and rules about subgrids.

Ports, admins and connecting#

Players find the server in the in-game server browser, or through Steam's server list using the IP and game port. The remote API (RemoteApiEnabled, RemoteApiPort, RemoteSecurityKey in the config) is used by Keen's remote client and some tools; leave it off unless you use it, and never expose it with a default key. Game server ports explained covers why a server can run perfectly well and still be invisible when one of the pair is closed.

Admins come from the Administrators list, as 17-digit SteamID64s. In game, an admin opens the admin screen with Alt+F10, which gives the cleanup tools, entity list, spectator and creative tools, and promotion of other players. The entity list is the single most useful moderation tool on the server: sort grids by PCU or by owner, find the abandoned 400-block mining ship at the edge of the system, and delete it.

Torch adds chat commands through plugins - Essentials is the one most servers install, for scheduled cleanup, grid management and restarts. Those commands come from the plugin, not the game, and their syntax is in the plugin's documentation.

Mods and the Workshop#

Space Engineers mods come from the Steam Workshop, and the dedicated server downloads them itself. They are listed in the config inside <Mods>, each with its Workshop id:

<Mods>  <ModItem FriendlyName="Example mod">    <Name>123456789.sbm</Name>    <PublishedFileId>123456789</PublishedFileId>  </ModItem></Mods>

The id above is a placeholder; take the real id from the Workshop page URL. Clients download the same mods automatically when they join, which makes Space Engineers one of the easier games for modded multiplayer - there is no manual mod parity to manage. Steam Workshop mods on dedicated servers explains how the server-side download works in general.

What to watch:

• Script mods run on the server and can be as expensive as any player-built contraption. A weapon-core or AI-ship framework is a performance decision, not just a content one.
• Block mods add PCU like vanilla blocks do, but some authors set values that do not reflect real cost.
• Mod order matters when two mods change the same definition; the later one wins.
• After a game update, broken mods typically stop the world loading or throw errors on join. Keep a list of what you run and read what to do when a mod update breaks before you need it.

Keeping sim speed at 1.0#

Sim speed is shown in the debug overlay (Shift+F11) and in Torch. Anything below about 0.8 feels sluggish; below 0.5 it is broken. The causes, roughly in order of how often they are the answer:

1. Subgrids colliding. Rotors, hinges and pistons that touch each other or the ground generate physics work every tick. Clang drives, rotor-based drills that clip into voxels, and pistons pushing against static grids are the classic offenders.
2. Too many active grids. Every powered, moving or recently touched grid is simulated. Debris from a battle and a field of abandoned rovers cost far more than their PCU suggests.
3. Programmable block scripts running every tick. EnableIngameScripts false is a blunt fix; a better one is a rule that scripts run at Update10 or Update100 rather than Update1.
4. Large `SyncDistance` and `ViewDistance`. Covered above.
5. Voxel changes. Heavy drilling on planets is expensive; huge drilling projects are better on asteroids.
6. Saving. A large world freezes for a moment at every autosave. Do not set AutoSaveInMinutes to 1.

The tools:

• Trash removal. TrashRemovalEnabled plus the trash flags clean up debris, unpowered and unnamed grids, and grids far from players after a delay. Tune the delay so a crashed ship survives long enough for its owner to come back for it.
• The entity list (Alt+F10) to find and remove the expensive grids.
• Scheduled restarts. Space Engineers leaks memory over long sessions and floating objects accumulate. A restart every 12 or 24 hours, at a quiet hour and with a warning, keeps it fresh - restart schedules that help explains how often is useful and how often is just disruption.
• Rules. Most public servers have written rules on subgrid counts and drone swarms. Limits enforce numbers; rules cover behaviour.

Saves, backups and moving a world#

A world is a folder: Saves\<WorldName>\ with Sandbox.sbc (world header and settings), Sandbox_config.sbc, SANDBOX_0_0_0_.sbs (the grids and entities, the big file), plus .sbsB5 binary copies and voxel files for modified asteroids and planets. The server keeps a Backup folder inside the save with timestamped copies, governed by the backup settings in the config.

To move a single-player world onto a server:

1. Find it in %AppData%\SpaceEngineers\Saves\<SteamID>\<WorldName>.
2. Stop the server.
3. Upload the whole folder into the server's Saves directory - SFTP and the file manager covers getting it there.
4. Point LoadWorld at its Sandbox.sbc, and make sure Sandbox_config.sbc has the limits you want, since single-player worlds often have none.
5. Start the server and check the log.

The built-in backup folder sits on the same disk as the world, so it protects against a corrupt save, not against losing the disk or the server. Keep copies off the machine and occasionally restore one. Backups that actually restore is the long version of that argument.

On RE:NODE, every game server gets backup slots stored off the machine they protect, restorable with a button, and a Schedules tab that can run a backup and a restart in order. Space Engineers is not in the catalogue, though, and its server needs Windows or Wine, which no game plan here provides - the VDS line is where you would build it yourself.

Troubleshooting#

The server is running but not in the browser. Check that both UDP ports are open, and that IP is 0.0.0.0 rather than a stale address. Join through Steam's server list by IP to separate a browser problem from a network problem.

Players are kicked with a mod or version mismatch. The game updated and the server did not, or a Workshop item updated mid-session. Update with SteamCMD and restart so the server fetches current mods.

Sim speed collapses when one player logs in. Something they own is only simulated when they are near it. Spectate their base with the admin tools and look for colliding subgrids.

The world loads with default settings. You edited the dedicated config, but the world's Sandbox_config.sbc still holds the old values. Edit both with the server stopped.

The server restarts every few hours. Memory exhaustion or a crashing mod. Read the last lines of the log before the restart; why your game server keeps restarting has the general checklist.

FAQ#

How many players can a Space Engineers server handle?

The setting goes well past what the simulation can usually carry. A well-run vanilla server holds 10-20 players comfortably; beyond that it depends almost entirely on what they build and how strictly you enforce limits and cleanup.

Does a Space Engineers server need a Steam account that owns the game?

No. The dedicated server downloads with anonymous SteamCMD login. Players need to own the game; the server does not.

What is a sensible PCU limit for a small group?

Per-player limits in the tens of thousands suit most groups of four to eight. Start lower than you think, because raising a limit later is easy and lowering it means deleting someone's work.

Can I run a Space Engineers server on Linux?

Only under Wine. It works for many people, but it is unsupported and occasionally breaks after updates. If uptime matters more than cost, run it on Windows.

Should I use Torch or the vanilla server?

Vanilla is fine for a private group. Torch is worth it for a public server, where plugins for cleanup, restarts and grid management save hours of admin time. Expect to wait for Torch updates after major game patches.