Mechanica Multiplayer Fix banner

Mechanica Multiplayer Fix

Created by: Oignon
4 devlogs
9h 53m 29s

A BepInEx mod for the game Mechanica (a survival and programming game abandoned during development, still unstable) that fixes multiplayer to make it playable. The mod makes multiplayer more stable, but it's still not a miracle fix; the entire gam…

A BepInEx mod for the game Mechanica (a survival and programming game abandoned during development, still unstable) that fixes multiplayer to make it playable. The mod makes multiplayer more stable, but it’s still not a miracle fix; the entire game would need to be rewritten. The code is such a mess of spaghetti and hardcoded logic that it would be a divine task (and working with decompiled code definitely doesn’t make it any easier).

This project uses AI

I used AI to help find faulty code and bugs in the game’s decompiled source code. It’s still a massive task, though.

Demo Repository

README

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Oignon
Oignon worked on Mechanica Multiplayer Fix
3 days ago
2h 21m logged

I took all the small independent patches that applied to the multiplayer management code and combined them into a major rewrite of the multiplayer class. Surprisingly, and for no apparent reason after doing that, my tests didn’t show any bugs. Therefore, I consider the mod finished. To be honest, I can’t really do more testing as other people’s availability is a significant constraint.

I added a README and a license to the project; it is now under LGPL-3.0.

Another random screenshot, but I didn’t have any friends on hand to illustrate the multiplayer. My mod isn’t doing this; it’s another mod I’m using to help me debug.

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Oignon
Oignon worked on Mechanica Multiplayer Fix
3 months ago
1h 42m logged

Seems I’ve fixed the infinite loading issue!

BUT, because why not, I found more major bugs. Most are fixed, but one is a real wall:

Under unknown conditions, the host gets timed out from their own server. I’ve ensured that if the server cuts out, clients now return to the menu with an error message. The base game didn’t handle this, leaving everyone stuck on infinite loads—mind-blowing, since handling connection loss is Networking 101.

Problem is, I can’t find the cause of the host timeout yet. Limited tester availability and the bug’s random nature are slowing me down.

Other issues: Laser Triggers are totally desynced 🤷, and conveyor belts are broken even in solo…

List of fixes/patchs applied:

  • Fix #12: Simplified (removed the code causing HarmonyX warnings)
  • Fix #13: Computer.ReceiveVirtualFunctionExecute() - Checks bounds before access
  • Fix #14: Computer.ReceiveVirtualEventInvoke() - Checks bounds
  • Fix #15: Computer.ReceiveVirtualObjectDestroy() - Checks bounds
  • Fix #16: ObjectManager.ApplyAllGUS() - Absorbs NullRefs during shutdown
  • Fix #17: Automatic recovery and menu return if the server crashes or disappears.
  • Fix #18: Proper disconnection handling (prevents infinite loading and shows clear error reasons).
  • Fix #19: Improved stability and error prevention for Spline/Curve calculations.
  • Fix #20: Added safety nets to prevent crashes during control point processing.
  • Fix #21: Final security layer to catch remaining errors in curve refreshing.

Sorry for the random image, I didn’t really have any ideas for a proper illustration for this devlog.

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Oignon
Oignon worked on Mechanica Multiplayer Fix
3 months ago
0h 30m logged

I wrote a Python script to check the date format in the save files to see if they’ve been patched by the mod

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Oignon
Oignon worked on Mechanica Multiplayer Fix
3 months ago
5h 19m logged

The main issue with Mechanica’s multiplayer is the infinite loading when a player joins a game that has already been created.

I conducted extensive tests and collected logs to identify the causes of this problem. I decompiled the game code and used profiling tools to pinpoint failure points.

This allowed me to discover several major issues, some of which were much harder to identify than others. So far, I have identified and theoretically fixed 12 problems, ranging from simple precautions to logging improvements to help identify new issues in the future.

I also wrote a PowerShell build script to automatically compile the mod and update it in the game.

The patches I applied are as follows:

  1. Date reading issue

    • Fixed saved dates with incompatible formats between players.

  2. New game creation issue

    • Corrected date formats when creating new games.

  3. Save sorting issue

    • Fixed incorrectly sorted saves caused by invalid date formats.

  4. Corrupted lobby data

    • Prevented crashes caused by corrupted Steam data.

  5. Inventory loading issue

    • Prevented crashes when loading inventories with invalid Steam IDs.

  6. Network errors

    • Logged network errors without interrupting sessions.

  7. Premature disconnection

    • Blocked unintentional disconnections when the game is not paused.

  8. Lobby transition issue

    • Prevented UI crashes during lobby state changes.

  9. Lobby refresh issue

    • Prevented crashes during lobby UI refreshes.

  10. Lobby connection issue

    • Prevented crashes when attempting to join a lobby.

  11. Player connect/disconnect issue

    • Prevented crashes during player connection or disconnection events.

  12. Disconnection without saving

    • Logged and validated premature disconnections.
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