OpenMU Browser Stack

MU Online in the browser. Server-side infrastructure to run MU Online via WebAssembly, using OpenMU as the game server.

What is this

Everything you need on the server side to bridge a WASM MU client to OpenMU:

• Game Server — OpenMU (C#/.NET) running via Docker with PostgreSQL
• WebSocket-TCP Proxy — Bridge between the browser (WebSocket only) and OpenMU (TCP)
• Web Server — Serves the WASM client with required headers (COOP/COEP)
• HTML Template — Ready to receive a compiled WASM client

flowchart LR
    subgraph Browser
        WASM[WASM Client]
    end

    subgraph Node.js
        WEB[Web Server\n:8080]
        PROXY[WS-TCP Proxy\n:7100]
    end

    subgraph Docker
        CS[Connect Server\n:44405]
        GS[Game Server\n:55901]
        PG[(PostgreSQL\n:5433)]
    end

    WASM -- HTTP --> WEB
    WASM -- WebSocket --> PROXY
    PROXY -- TCP --> CS
    PROXY -- TCP --> GS
    CS --- PG
    GS --- PG

Loading

Connection flow:

1. Client opens WebSocket to proxy → proxy connects TCP to Connect Server (:44405)
2. Connect Server sends ConnectionInfo (C1 F4 03) with Game Server IP:port
3. Proxy rewrites the IP:port to its own address, stores the real target
4. Client reconnects via WebSocket → proxy routes TCP to Game Server (:55901)

Status

Component	Status
WebSocket-TCP Proxy	Implemented, not tested end-to-end
Web Server (static + COOP/COEP)	Implemented
MU Packet Parser (C1/C2/C3/C4)	Implemented
ConnectionInfo Rewriter (F4 03)	Implemented
OpenMU via Docker	Configured
WASM Client	Pending — see WASM Client

Note: No compatible WASM client exists yet. The proxy and packet parser are implemented but have not been tested with a real game session.

Quick Start

Prerequisites

• Node.js 22+
• Docker and Docker Compose

1. Clone and install

git clone https://github.com/your-username/openmu-browser-stack.git
cd openmu-browser-stack
npm install
cp .env.example .env

2. Start OpenMU

docker compose up -d

This starts:

• PostgreSQL 16 on port 5433
• OpenMU with auto-start
  • Admin panel: http://localhost:8090
  • Connect Server: port 44405
  • Game Servers: ports 55901-55906
  • Chat Server: port 55980

3. Start the proxy and web server

npm start

Or separately:

npm run proxy   # WebSocket proxy on port 7100
npm run serve   # Web server on port 8080

4. Open

Go to http://localhost:8080. You will see a placeholder page — the WASM client is not included. See WASM Client for the next step.

WASM Client

This repository does not include the game client. You need to compile a MU Online client to WebAssembly.

Recommended client: MuMain

sven-n/MuMain is the best candidate:

• C++ with OpenGL — Emscripten maps OpenGL ES to WebGL natively
• Compatible with OpenMU (standard MU protocol C1/C2/C3/C4)

Required work

Task	Description
OpenGL 1.x → OpenGL ES 2.0	Replace glBegin/glEnd with VBOs + GLSL ES shaders
Networking .NET → C++	Rewrite ClientLibrary (.NET AOT) in pure C++
Win32 → SDL2/Emscripten	Replace windows.h with SDL2 (cross-platform)
Audio → Web Audio	Replace DirectSound/wzAudio with OpenAL or SDL_mixer
Game loop	Adapt to emscripten_set_main_loop()
Assets	Package BMD/OZJ/OZB into Emscripten's .data file

Integrating the compiled client

1. Compile with Emscripten (outputs .js, .wasm, .data)
2. Copy to public/
3. Add <script async src="YourClient.js"></script> to public/index.html
4. Module.websocket.url already points to the proxy (ws://127.0.0.1:7100)

MU Online Protocol

The proxy understands MU packet framing:

Header	Size	Encryption
C1	1 byte (max 255)	None
C2	2 bytes BE (max 65535)	None
C3	1 byte	SimpleModulus / XOR32
C4	2 bytes BE	SimpleModulus / XOR32

The proxy is transparent to encryption. The only exception is the ConnectionInfo packet (C1 F4 03), whose IP:port is rewritten to redirect connections through the proxy.

Structure

openmu-browser-stack/
├── docker-compose.yml          # OpenMU + PostgreSQL
├── .env.example                # Configuration template
├── package.json
├── public/
│   └── index.html              # HTML template for the WASM client
└── src/
    ├── proxy/
    │   ├── index.js            # Proxy entry point
    │   ├── ws-server.js        # WebSocket↔TCP bridge
    │   ├── tcp-client.js       # TCP client wrapper
    │   ├── packet-parser.js    # MU packet framing (C1/C2/C3/C4)
    │   └── packet-rewriter.js  # ConnectionInfo (F4 03) rewriter
    └── web/
        └── server.js           # Static file server

Configuration

Copy .env.example to .env:

Variable	Default	Description
WS_PORT	7100	WebSocket proxy port
WEB_PORT	8080	Web server port
MU_CONNECT_HOST	127.0.0.1	Connect Server host
MU_CONNECT_PORT	44405	Connect Server port
MU_GAME_HOST	127.0.0.1	Game Server host (for IP remapping)
PROXY_PUBLIC_HOST	127.0.0.1	Proxy public IP

Troubleshooting

Port 7100 in use (macOS): Disable AirPlay Receiver in System Settings → General → AirDrop & Handoff, or change WS_PORT.

OpenMU won't start: docker compose down -v && docker compose up -d to clean up and restart.

License

MIT