Fixing a Space Engineers server starts by identifying which failure you have. If the world keeps players connected but actions arrive late or characters and ships snap backward, the dedicated server is struggling with simulation load. If players time out, are dropped during the handshake, or cannot find the world, test the network path, ports, firewall, VPN and server configuration instead. A reliable diagnosis uses a no-mod test, verifies the configured UDP listen port, compares different internet connections, and captures both client and server logs before changing several variables at once.
Why is my Space Engineers server lagging?
Most complaints described as “lag” are one of two different problems: simulation overload or a failed network connection. They need different fixes. Keen Software House explains that performance depends on world complexity and the host computer; every additional object can require more computation and memory. An overloaded dedicated server can produce rubber-banding, where the server repeatedly corrects a player’s position or actions.
Simulation lag can continue even when every player remains connected. Network trouble appears as a timeout, a failed handshake, a disconnect, or a server that never appears in the browser. Start with the symptom rather than changing ports or buying hardware at random.
How can I tell simulation lag from a timeout or missing server?
| What players see | Most likely cause | First test |
|---|---|---|
| Everyone remains online, but movement, block placement or tools respond late; ships jump back to earlier positions. | Server simulation overload or insufficient CPU/RAM. | Pause heavy activity, remove floating objects and run a no-mod world. Watch whether synchronization recovers. |
| One player is dropped while others continue normally. | That player’s route, Wi-Fi, VPN, firewall or antivirus filtering. | Have the affected player try wired Ethernet or a mobile hotspot. |
Several players receive a timeout or Peer2Peer_ConnectionFailed. |
Port forwarding, host firewall, router rules or launch configuration. | Check the configured ServerPort, forward its UDP port and inspect the logs. |
| The server is reachable by Direct Connect but absent from the server list. | Server-list registration, Steam/EOS mode, SteamPort or filtering software. |
Confirm the endpoint shown by Join Game > LAN and compare the network-mode settings. |
| The server will not start and reports that socket use is already permitted. | Another process is already bound to the same port. | Stop the competing process or assign a unique port, then restart with the required permissions. |
How do I stop rubber-banding caused by server simulation overload?
Treat rubber-banding as a server workload problem until a controlled test proves otherwise. A faster client GPU cannot repair a simulation that the dedicated host cannot calculate on time.
Reduce the activities that create the most work
Make one change at a time and observe the same area of the world. Temporarily pause or remove:
- Large drilling operations and multiple drills working at once.
- Rows of launchers firing simultaneously.
- Heavy refinery and assembler production running in parallel.
- Large numbers of floating objects, dropped components or debris.
- Dense collision scenes, wreck piles and complicated mechanical interactions.
- Very large ships, stations or other structures with many functional blocks.
- Spotlights and other effects when they are being used in unusually large numbers.
These changes are diagnostic rather than permanent design rules. If the server becomes responsive after a particular activity stops, reintroduce that activity at a smaller scale and monitor the result.
Run a clean configuration test
Back up the world, then start a copy with no mods and no custom launch options on either the server or the client. Keen Software House QA specifically recommends this isolation step when connections are unstable. If the clean world behaves normally, add mods and launch options back one at a time. The first addition that brings the problem back is the useful lead; adding everything simultaneously hides it.
Do not use client FPS as a server-health meter
Frames per second describe how smoothly one player’s computer renders the game. The dedicated server’s physics and world simulation are separate. A player can have low FPS while the simulation is healthy, or see smooth local rendering while the server is calculating too slowly. Lower client graphics settings only address the former; reducing world workload or improving the host addresses the latter.
What hardware and bandwidth does a dedicated server need?
Keen Software House’s current dedicated-server page lists the following guidance. The page does not display a publication year, so treat the figures as current-page recommendations and recheck them after major game updates.
| Resource | Minimum listed guidance | Recommended for public hosting | How to interpret it |
|---|---|---|---|
| CPU clock | 3.2 GHz | 4.5 GHz | Simulation is sensitive to sustained single-thread speed and the workload generated by the world. |
| Logical cores | 3 | 3 | The recommendation does not increase the listed core count; clock speed and actual workload still matter. |
| Memory | 6 GB RAM | 10 GB RAM | More objects, scripts and loaded content increase memory pressure. |
| Bandwidth | 5 Mbps | Not separately stated | The page lists 5 Mbps as a minimum; it does not give a public-hosting target above that figure. |
| Public address | Not required in the minimum row | Static IP | A stable address makes an externally reachable server easier to publish and troubleshoot. |
A dedicated server runs without the rendering and audio/visual effects of a player-hosted game and is intended for long-running multiplayer sessions. Keen describes it as letting players connect to a third-party host instead of relying on a player’s peer-to-peer session. Those properties improve availability, but they do not make an overloaded world inexpensive to simulate.
How do I fix Peer2Peer_ConnectionFailed and timeout errors?
Work from the outside of the network inward. Keep the server in a no-mod, no-custom-option state until the basic connection works; otherwise a configuration problem and a network problem can look identical.
- Record the exact symptom. Note whether the failure happens before the world loads, after a player has joined, or only when the server is listed. Record the network mode, the configured ports and the time of one reproducible attempt.
- Verify the address and port in the server configuration. Open
SpaceEngineers-Dedicated.cfgand check the configured<IP>and<ServerPort>. The default listen port in Keen’s guide is UDP27016, but use the value actually configured on your server if it has been changed. - Forward the listen port. Create a router rule that forwards the configured UDP port to the dedicated-server machine’s private address. A rule aimed at the wrong internal computer will appear open in the router while the game remains unreachable.
- Allow the same traffic in the host firewall. Permit incoming UDP on the configured port. On a restrictive Windows Server installation, also inspect outbound and ephemeral-port rules; a Keen QA case required TCP and UDP ports
49152–65535in addition to the main game port. - Temporarily remove network filters for a controlled test. Disable a VPN, antivirus network inspection and host/client firewall filtering only long enough to reproduce the connection attempt. Restore protection immediately and replace the broad test with narrow allow rules for the game and its required ports.
- Try a different route. Ask the affected player to compare Wi-Fi, wired Ethernet and a mobile hotspot. A Cat 6 Ethernet cable is useful for this diagnostic comparison because it removes local wireless interference; it cannot cure a server whose simulation is overloaded.
- Apply the Steam launch-option check. For a
Peer2Peer_ConnectionFailedcase, Keen QA recommends testing the dedicated-server launch options with-steam. Keep a record of the original options so you can revert the test cleanly. - Repeat with one player and one clean world. If a single external player can join the clean configuration, add the normal mods and options incrementally. If nobody can join, keep investigating the route, firewall and port rules rather than the world contents.
Which ports, firewall rules and router settings matter?
Use the configured UDP ServerPort
Keen’s official guide identifies UDP as the game transport and gives 27016 as the default listen port. Forward that port from the router to the server and permit incoming UDP on the host. If you changed ServerPort, forwarding 27016 will not help; the router, firewall and connection endpoint must all use the changed value.
Check restrictive ephemeral-port policies
Some Windows Server environments allow the main game port but block the temporary ports used during a session. In a 2025 Keen Software House QA troubleshooting case, the documented range was TCP and UDP 49152–65535. Treat that range as an environment-specific check, not as a replacement for forwarding the configured listen port.
Resolve port conflicts before testing clients
Do not run two server instances on the same port. An error such as Only one usage of each socket address … is normally permitted
indicates that another process already owns the address. Stop the competing process or assign a unique port to the second instance, then start the manager with the administrator permissions it requires.
How do I isolate VPN, antivirus, Wi-Fi and router problems?
A connection that works from one network but not another points to the path, not automatically to the game world. Use a short, repeatable test:
- Leave the server world unchanged and invite one affected player.
- Test once with the player’s normal Wi-Fi.
- Test again through wired Ethernet if available.
- Test through a mobile hotspot.
- On the host, repeat with VPN and antivirus network filtering disabled only for the controlled attempt.
- Restore security software and create specific exceptions instead of leaving protection disabled.
If the hotspot succeeds while the home connection fails, provide the home router or internet provider with the destination port and failure time. If every route fails, return to ServerPort, firewall, launch options and logs. A wired test is evidence about the path; it is not a general performance upgrade for simulation.
Why is my server reachable by Direct Connect but missing from the server list?
This is a discovery or registration problem, not proof that the world itself is unreachable. Use the game’s list to expose the endpoint, then test that endpoint independently.
- Open Join Game > LAN and identify the public
steam://IP:portendpoint shown for the server. - Have a player outside the host’s local network use Direct Connect with that endpoint.
- If Direct Connect succeeds, verify that
ServerPortandSteamPortcontain the intended values and are not being claimed by another process. - Confirm that only one network mode, Steam or EOS, is enabled for the intended setup. A mixed or partially configured mode can prevent normal listing.
- Check whether firewall, antivirus or VPN software is blocking registration traffic even though the direct session is allowed.
Do not change several ports at once. Keep a written record of the old values, make one adjustment, restart the server and test the list again.
What does 0.0.0.0 mean in SpaceEngineers-Dedicated.cfg?
An address of 0.0.0.0 normally tells the server to bind to all available network interfaces. That is usually appropriate on a host with one or more active adapters. Keen QA notes that some local-network arrangements may instead require the public IP in the configuration; test the actual interface layout rather than replacing the value blindly.
When changing the address, make sure the router forwards to the same machine and that the public endpoint is not confused with the host’s private LAN address. A successful local connection does not prove that an external player can traverse the router.
Where are the Space Engineers client and dedicated-server logs?
Logs are the next step when port and clean-configuration checks do not identify the fault. Reproduce the problem once, save the files before launching the game again, and include the exact time of the failed attempt.
- Client log:
C:Users{YOUR WINDOWS USERNAME}AppDataRoamingSpaceEngineersSpaceEngineers.log. Keen’s troubleshooting guidance notes that this file is overwritten on each launch. - Dedicated-server logs: the
SpaceEngineersDedicatedroaming folder used by the Steam setup.
Send both sides of the event when requesting help. A useful report identifies the network mode, configured ServerPort and SteamPort, whether the clean test was successful, the enabled mods and launch options, and the timestamp shared by the client and server logs.
When should I move the server to managed hosting?
Consider managed hosting when the local machine repeatedly fails port forwarding, cannot meet the CPU/RAM or bandwidth guidance, or cannot remain online for the group’s schedule. Keen Software House lists GTX Gaming as an official PC host and Nitrado as an official Xbox host. Check the provider’s current price, region availability, hardware allocation and partner terms before committing; those details can change independently of the game’s documentation.
Moving hosts does not remove world-load limits. Export the world, reproduce the issue on a no-mod copy, and add content back gradually after migration. This prevents a heavy world or incompatible mod from being mistaken for a hosting fault.
What is the fastest complete troubleshooting order?
Use this checklist when you need a single pass that covers both kinds of failure:
- Classify the symptom as simulation delay, a timeout/disconnect, or a missing list entry.
- Back up the world and test with no mods and no custom launch options.
- For simulation delay, pause drills, launchers, production, collisions, floating objects and complex structures.
- Compare the host’s CPU, RAM and bandwidth with Keen’s listed guidance.
- For connection errors, verify
ServerPort, forward its UDP port and allow it through the host firewall. - On restrictive Windows Server systems, inspect TCP/UDP ephemeral ports
49152–65535. - Remove VPN and network-filtering variables for one controlled test, then compare Wi-Fi, Ethernet and a hotspot.
- For
Peer2Peer_ConnectionFailed, test-steamand confirm<IP>and<ServerPort>. - For a missing list entry, test the public
steam://IP:portendpoint and verifySteamPortplus the single selected network mode. - Save the client and server logs after one reproduction, then decide whether the host or the world configuration needs to change.
Frequently Asked Questions
Will a better graphics card fix rubber-banding on a dedicated server?
Usually not. A graphics upgrade can raise a player’s local frame rate, but rubber-banding caused by delayed physics calculations requires reducing the server’s world workload or providing a faster, adequately provisioned host CPU and memory.
Can I leave the server’s firewall disabled after a successful test?
No. Disabling it is only a diagnostic experiment. Restore the firewall and create narrowly scoped rules for the configured game traffic so unrelated services are not exposed.
Why does my connection work locally but fail for friends outside the house?
A local test can stay inside the LAN and never exercise the router’s public translation. External players require the router’s UDP forwarding, the host firewall rule and a reachable public endpoint; test from a separate network such as a mobile hotspot.
What should I do before changing the server port?
Record the current ServerPort, SteamPort, router rule, firewall rule and launch options. Change one value, update every dependent rule and endpoint, restart the server, and keep the old settings available for rollback.