Steel Proxy - Minecraft Server Proxy

A Minecraft proxy server for Steel server instances, allowing players to switch between multiple backend servers using the /server command.

Features

• Multi-Server Support: Connect multiple Steel backend servers
• Server Switching: Use /server <name> to switch between servers
• Transfer Packet: Uses Minecraft 1.20.5+ Transfer packet for seamless switching
• Offline Mode: Currently supports offline mode (online mode coming soon)
• Bidirectional Packet Forwarding: Minimal latency with immediate forwarding

Architecture

[Minecraft Client] <---> [Steel Proxy] <---> [Backend Server 1]
                              |
                              +-----------> [Backend Server 2]

How It Works

1. Client connects to proxy (appears as normal Minecraft server)
2. Proxy authenticates player (offline mode - uses client-provided UUID)
3. Proxy connects to default backend server (offline mode)
4. Bidirectional packet forwarding begins
5. When player types /server <name>:
   • Proxy intercepts the command
   • Sends Transfer packet to client with proxy's own address
   • Client disconnects and reconnects to proxy
   • Proxy connects to new backend server
   • Forwarding resumes with new server

Configuration

Create proxy-config.toml:

# Address to bind the proxy to
bind_address = "0.0.0.0"

# Port to listen on
bind_port = 25565

# Enable online mode (currently only offline mode supported)
online_mode = false

# Default server for new connections
default_server = "survival"

# Backend servers
[backends.survival]
address = "127.0.0.1"
port = 25566
description = "Survival Server"

[backends.creative]
address = "127.0.0.1"
port = 25567
description = "Creative Server"

Building

cargo build --release

Running

1. Start your backend Steel servers in offline mode on their configured ports
2. Run the proxy:

   cargo run --release

3. Connect your Minecraft client to the proxy address (localhost:25565)

Usage

Once connected:

• You start on the default server (configured in proxy-config.toml)
• Type /server survival to switch to the survival server
• Type /server creative to switch to the creative server

Current Status

✅ Implemented

• CTransfer packet added to steel-protocol
• Proxy crate structure created
• Configuration system (TOML-based)
• Client connection handler (offline mode)
• Backend server connector (offline mode)
• Bidirectional packet forwarding framework
• /server command interception
• Transfer packet server switching logic

🚧 In Progress

• Fix remaining compilation errors (packet encoding issues)
• Test with actual Steel backend servers
• Handle server switch state persistence

📋 Future Enhancements

• Online mode support (Mojang authentication)
• Player state caching between servers
• Connection pooling to backend servers
• Tab completion for /server command
• Permission system (which servers players can access)
• MOTD/Player list from all backend servers
• Fallback server on disconnect
• Metrics and monitoring

Known Issues

1. Compilation errors: Some packet encoding methods need adjustment for ServerPackets vs ClientPackets
2. Server switch persistence: Need to store which server player wants after Transfer packet
3. No compression/encryption: Offline mode only, no packet compression or AES encryption

Technical Details

Dependencies

• steel-protocol: Minecraft protocol implementation
• steel-utils: Utility functions and codecs
• steel-crypto: Cryptographic operations (not fully utilized yet)
• tokio: Async runtime
• serde/toml: Configuration parsing
• anyhow: Error handling

Packet Flow

Client → Proxy → Backend:

1. Proxy receives encrypted packet from client (if online mode)
2. Proxy decrypts packet
3. Check for /server command
4. Forward all other packets unchanged to backend

Backend → Proxy → Client:

1. Proxy receives packet from backend (unencrypted, offline mode)
2. Forward packet unchanged to client
3. Re-encrypt for client (if online mode)

Server Switching

When /server <name> is detected:

1. Validate server exists in config
2. Send CTransfer packet with proxy's address/port
3. Client disconnects
4. Client reconnects to proxy
5. New ClientHandler created
6. Connect to requested backend server (TODO: need state storage)
7. Resume packet forwarding

License

Part of the SteelMC project.