Open.mp Launcher

A cross-platform server browser and launcher for open.mp / SA-MP. Built primarily for Linux (via Wine). It should work on Windows too, I hope.

Why?

The official open.mp launcher does not officially support Linux. This one handles the Wine prefixes, DLL overrides, and registry keys automatically.

Architecture

This isn't just a wrapper anymore. It includes:

• Custom C++ Injector: A native simple-injector.exe compiled from source that handles the DLL injection process (loads samp.dll and omp-client.dll in a suspended state). So we don't depend on the omp-launcher to handle the injection.
• Zero-Dependency Networking: Custom UDP implementation of the SA-MP query protocol (i/c/r opcodes).
• Asset Management: Automatically hash-checks and downloads correct SA-MP versions (0.3.7-R5, DL, etc.) and assets (sampgui.png, fonts).
• Wine Automation: Automatically detects your Wine prefix, sets WINEDLLOVERRIDES, and handles the registry for PlayerName.

Prerequisites

If you are on Linux and want to build this, you need the cross-compiler for the injector.

Linux (Debian/Ubuntu)

sudo apt install wine mingw-w64

Windows

You need MinGW or MSVC. But if you're on Windows just run the build command, it handles itself.

Development

I use pnpm.

# Install dependencies
pnpm install

# Build the C++ injector and fetch assets
pnpm run prepare-build

# Run in dev mode
pnpm run dev

Building

# Build for Linux (AppImage, deb, pacman)
pnpm run build:linux

# Build for Windows (NSIS)
pnpm run build:win

How the Injector Works

The launcher compiles injector/injector.cpp using i686-w64-mingw32-g++ (on Linux) or g++ (on Windows).

When you click play:

1. It validates the gta_sa.exe version.
2. It ensures the correct samp.dll hash.
3. It spawns the injector, which creates the GTA process in CREATE_SUSPENDED mode.
4. It injects the DLLs via VirtualAllocEx / CreateRemoteThread.
5. It resumes the thread.

PRs and issues are appreciated.