Bopl Battle Fixes (BoplFix)

An unofficial BepInEx mod for Bopl Battle that restores fast direct LAN / peer-to-peer play and adds a few quality-of-life fixes.

TL;DR: Online matches - even two PCs in the same room - get forced through a distant Steam relay, causing a constant ~250 ms ping and rubber-banding. This mod makes the game connect directly, so a LAN game drops back to ~1 ms. It also remembers your keybindings and default powerups between launches.

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Features

Fix	What it does
Direct LAN / P2P	Restores direct (ICE) connections instead of relay-only, so peers on the same network connect directly (~1 ms instead of ~250 ms). The Steam relay stays as a fallback for normal internet play.
Keybinding memory	Remembers your custom keyboard/mouse keybindings across launches (the game normally forgets them every time).
Default powerup memory	Remembers your last chosen abilities/powerups and pre-selects them next launch.
In-game net overlay	Press F8 in an online match to show each peer's live ping and whether the connection is DIRECT (LAN) or via RELAY - so you can see the fix working.
"Mod loaded" badge	A small + BoplFix badge above the main-menu version number, so it's obvious the mod is active.

Everything is toggleable in the config file, and all logging is off by default.

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Why LAN was broken (root cause)

Bopl Battle uses Steam's modern SteamNetworkingSockets P2P API (CreateRelaySocket / ConnectRelay). For two peers to connect directly, Steam uses ICE (the same NAT-traversal tech as WebRTC), and ICE is implemented in a separate native library, steamwebrtc64.dll. Three things were wrong:

1. The ICE engine couldn't even load. Bopl never shipped steamwebrtc64.dll next to its own steam_api64.dll, and Steam doesn't add its own install folder to the game's DLL search path. So Steam's networking failed to load the engine (ICE failed: Failed to load steamwebrtc64.dll / No ICE session factory) and every connection - including same-room LAN - silently fell back to a Steam Datagram Relay server (Remote host is in data center 'lax', ~228 ms). No amount of config can fix this, which is why it looks unfixable: there is no engine to do direct connections with.
2. ICE wasn't enabled. Even with the engine present, the game never sets P2P_Transport_ICE_Enable, and on Steam the default is relay-only (IP addresses aren't shared between peers - an anti-DoS measure).
3. No STUN server list. Valve's docs note "if you set this to an empty string, NAT piercing will not be attempted", and it's empty by default, so ICE never gathers candidate addresses.

The mod fixes all three: it copies steamwebrtc64.dll from your Steam client into the game folder (so the engine loads), then sets P2P_Transport_ICE_Enable = All and a P2P_STUN_ServerList. The game's last build is from mid-2025, so the regression was triggered by a Steam-side change, not a game patch.

This is purely a transport change - packet contents are identical, so it cannot cause desyncs in the game's lockstep netcode. The STUN servers are only used to discover addresses; actual LAN traffic stays on the LAN.

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Requirements

• Bopl Battle (Steam) on Windows (64-bit), launched through Steam at least once (so steamwebrtc64.dll exists in your Steam client folder - the mod copies it from there).
• For the LAN fix, both players must install the mod - direct (ICE) connections require both peers to have a working ICE engine and to offer their addresses. (The other fixes are local and don't require the other player to have the mod.)
• Two different Steam accounts (you can't run one account on two PCs at once).

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Install

Do this on BOTH PCs for the LAN fix. Pick whichever option you like - all three install the same thing.

Option 1 - installer (easiest)

Download and run BoplFix-Installer.exe (~0.8 MB). It finds your Bopl Battle install automatically, plus the free Bopl Battle Demo if you have it, and installs into each, asks you to confirm first. If a copy sits in a protected folder (e.g. Program Files, where the Demo usually lives) it automatically requests administrator rights (UAC). Close the game first if it's open.

It uses Windows' built-in PowerShell, so there's nothing else to install. Being unsigned, Windows SmartScreen may show "Windows protected your PC" - click More info -> Run anyway. If your antivirus is strict about self-extracting installers, just use Option 2 instead (same mod).

Option 2 - one-click bundle (no installer)

1. Close Bopl Battle.
2. Open the game folder: in Steam, right-click Bopl Battle -> Manage -> Browse local files (the folder containing BoplBattle.exe).
3. Extract everything from BoplFix-v1.0.0.zip into that folder. When done, winhttp.dll and a BepInEx folder sit next to BoplBattle.exe.
4. Launch the game once. Done.

Option 3 - just the plugin (if you already have BepInEx 5 x64)

Drop BoplFix.dll into BepInEx\plugins\.

The three downloads are the same mod in different wrappers: the installer does it for you, the zip is the mod plus the BepInEx loader to extract manually, and the dll is only the mod (for people who already run BepInEx).

The mod copies steamwebrtc64.dll into the game folder automatically on first launch - you don't need to find or copy any DLL yourself.

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Uninstall

Easiest: run BoplFix-Installer.exe again. When it detects the mod is already installed it asks Reinstall / Uninstall / Cancel - choose Uninstall. It removes the mod, and if BoplFix was your only BepInEx mod it removes the BepInEx loader too, returning the game to vanilla. If you have other BepInEx mods (even ones tucked in their own subfolder), it leaves BepInEx and those mods alone, and only does a full vanilla reset if you explicitly confirm. (It auto-elevates if the folder needs admin rights.)

Manually: delete BepInEx\plugins\BoplFix.dll (and BepInEx\config\com.boplfix.cfg). To remove the loader entirely as well, also delete the BepInEx folder, winhttp.dll, doorstop_config.ini and .doorstop_version from the game folder - but only if you have no other BepInEx mods. (Leaving the copied steamwebrtc64.dll behind is harmless - it just lets Steam do direct connections.)

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Configuration

After the first launch, settings are at BepInEx\config\com.boplfix.cfg:

[Netcode]
EnableDirectP2P = true        # the LAN fix (copy ICE engine + enable ICE)
PreferDirectOverRelay = true  # bias toward the fast direct route
StunServerList = stun.l.google.com:19302,stun1.l.google.com:19302  # activates ICE candidate gathering

[QualityOfLife]
SaveKeybindings = true        # remember keyboard/mouse binds
SaveDefaultPowerups = true    # remember chosen abilities

[Badge]
ShowBadge = true              # "+ BoplFix" badge above the main-menu version number
BadgeSizePercent = 24         # badge size as a % of the version number
BadgeColorHex = 1B5E20        # badge colour (hex RGB, no '#'); e.g. 0A4DA0 blue, B5530A orange

[Diagnostics]
ShowNetOverlay = false        # in-game ping + DIRECT/RELAY overlay; press F8 in a match to toggle
VerboseLogging = false        # troubleshooting only - see below

Enabling verbose logging (troubleshooting)

Logging is off by default for clean, quiet play. If a direct connection isn't forming and you want to see why, set:

[Diagnostics]
VerboseLogging = true

Relaunch, reproduce the match, then read BepInEx\LogOutput.log. With it on, the mod writes the full Steam ICE/relay negotiation plus a per-peer [Route] block (ping + route) every few seconds, which shows exactly whether the connection went DIRECT or via RELAY and why. Set it back to false for normal play - the LAN fix itself is always on regardless of this setting.

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Verifying the LAN fix

See TESTING.md for the full 2-PC procedure and which log lines confirm a direct connection. The quickest check: press F8 during an online match and look for DIRECT (LAN) with a low ping.

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Build from source

Requires the .NET SDK. References resolve against your local game install.

# default game path is D:\SteamLibrary\steamapps\common\Bopl Battle
dotnet build src/BoplFix/BoplFix.csproj -c Release

# different install location:
dotnet build src/BoplFix/BoplFix.csproj -c Release -p:GameDir="C:\Program Files (x86)\Steam\steamapps\common\Bopl Battle"

The output BoplFix.dll lands in src/BoplFix/bin/Release/. On Windows, build.ps1 produces all three release artifacts in dist/: the plugin DLL, the one-click bundle zip, and the installer .exe (built with the built-in IExpress, wrapping installer/install.ps1 + the bundle - ~0.8 MB).

The mod targets netstandard2.1 and references BepInEx, 0Harmony, and the game's Assembly-CSharp / Facepunch.Steamworks.Win64 / UnityEngine / Unity.InputSystem assemblies.

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How it works (technical)

• LAN fix - In Awake, EnsureWebRtcDll() copies steamwebrtc64.dll from the Steam client (located via HKCU\Software\Valve\Steam\SteamPath, with %ProgramFiles% fallbacks) into the game folder if it isn't already there, so Steam's networking can load the ICE engine. Then a Harmony postfix on Steamworks.SteamClient.Init sets the global config values P2P_Transport_ICE_Enable = 0x7fffffff, P2P_Transport_ICE_Penalty = 0, and P2P_STUN_ServerList via the Facepunch wrapper.
• Keybindings - Saved as InputControl.path strings (PlayerPrefs) when a rebind completes (KeyBindButton.UpdateKeybind), and re-applied for keyboard players in InputUpdater.Init if they haven't rebound this session.
• Powerups - The chosen ability index is saved (SelectAbility.UpdatePlayerInit) and pre-selected when a player freshly joins character-select (CharacterSelectBox.OnEnterSelect).
• Overlay / badge - The overlay reads each peer's Connection.DetailedStatus() to classify the route (a "data center" line = RELAY; a private IP = DIRECT/LAN). The badge is a standalone text element placed relative to the rendered version number in a postfix on printText.Awake (it never modifies the version label, and runs after Constants.version is captured, so lobby version-matching is untouched).

Per-frame work (overlay, F8, route logging) is driven from a Harmony hook on SteamManager.Update, because this game never ticks a BepInEx plugin's own Update()/OnGUI(). The LAN-fix patch is applied first and in isolation, so a failure in any other patch can never disable it.

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Compatibility & safety

• Does not modify any game files; it's a standard BepInEx plugin. (It does copy Valve's own steamwebrtc64.dll into the game folder to enable direct connections.)
• The LAN fix only changes how packets are routed, not their contents - safe for the deterministic lockstep netcode (no desyncs).
• Keybindings and powerup defaults are local UI state and are never sent over the network.

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Disclaimer

Unofficial and not affiliated with or endorsed by the developer of Bopl Battle. Provided as-is under the MIT License (see LICENSE). It only contains original mod code - no game assets.