RyuLdn Protocol

RyuLdn Protocol

This page documents the RyuLdn network protocol used to communicate with the server.

Overview

RyuLdn is a binary protocol over TCP. All multi-byte integers are little-endian.

Packet Structure

┌─────────────────────────────────────────┐
│ Header (4 bytes)                        │
├─────────────────────────────────────────┤
│ Magic (2 bytes): 0x524C ("RL")          │
│ Type (1 byte): PacketType enum          │
│ Reserved (1 byte): 0x00                 │
├─────────────────────────────────────────┤
│ Payload (variable)                      │
│ Structure depends on packet type        │
└─────────────────────────────────────────┘

Packet Types

Value	Name	Direction	Description
0x01	Passphrase	C→S	Authentication
0x02	Connected	S→C	Connection confirmed
0x03	SyncNetwork	S→C	Network state sync
0x04	Disconnect	Both	Disconnection notice
0x10	Scan	C→S	Request network scan
0x11	ScanResponse	S→C	Scan results
0x20	CreateAccessPoint	C→S	Create network
0x21	CreateAccessPointResponse	S→C	Create result
0x30	Connect	C→S	Join network
0x31	ConnectResponse	S→C	Join result
0x40	SetAcceptPolicy	C→S	Set join policy
0x50	SetAdvertiseData	C→S	Update advertisement
0x60	Reject	C→S	Reject a connection
0x70	ProxyData	Both	Game data relay
0x80	ProxyDataBroadcast	Both	Broadcast data

Authentication Flow

Client                                Server
  │                                      │
  │──── Passphrase ─────────────────────▶│
  │     (game_id, ssid, etc.)            │
  │                                      │
  │◀──── Connected ──────────────────────│
  │      (assigned node_id)              │

Packet Definitions

Passphrase (0x01)

Sent by client after TCP connection.

struct PassphrasePacket {
    u32 magic;          // "RL" + type + reserved
    u64 game_id;        // Title ID
    u8 ssid[32];        // Network SSID
    u8 passphrase[32];  // Network passphrase
};

Connected (0x02)

Sent by server to confirm connection.

struct ConnectedPacket {
    u32 magic;
    u8 node_id;         // Assigned node ID (0-7)
};

SyncNetwork (0x03)

Sent by server when network state changes.

struct SyncNetworkPacket {
    u32 magic;
    NetworkInfo network_info;  // Full network state
};

Scan (0x10)

Request to scan for available networks.

struct ScanPacket {
    u32 magic;
    ScanFilter filter;  // Optional filter criteria
};

ScanResponse (0x11)

Contains discovered networks.

struct ScanResponsePacket {
    u32 magic;
    u16 network_count;
    NetworkInfo networks[];  // Variable length
};

CreateAccessPoint (0x20)

Request to create a new network (host).

struct CreateAccessPointPacket {
    u32 magic;
    SecurityConfig security;
    UserConfig user;
    NetworkConfig network;
};

Connect (0x30)

Request to join an existing network.

struct ConnectPacket {
    u32 magic;
    u8 network_id[16];   // Network to join
    ConnectData data;    // Connection data
};

ProxyData (0x70)

Game data relay between nodes.

struct ProxyDataPacket {
    u32 magic;
    u8 source_node;      // Sender node ID
    u8 dest_node;        // Destination node ID (0xFF for all)
    u16 data_size;       // Payload size
    u8 data[];           // Game data
};

ProxyDataBroadcast (0x80)

Broadcast game data to all nodes.

struct ProxyDataBroadcastPacket {
    u32 magic;
    u8 source_node;
    u16 data_size;
    u8 data[];
};

NetworkInfo Structure

struct NetworkInfo {
    u8 network_id[16];           // Unique network ID
    Ssid ssid;                   // Network SSID
    SecurityConfig security;     // Security settings
    UserConfig host_user;        // Host information
    u8 node_count;               // Current players
    u8 node_count_max;           // Maximum players
    NodeInfo nodes[8];           // Player information
    u16 advertise_data_size;     // Advertisement size
    u8 advertise_data[384];      // Game advertisement
};

Error Handling

If a malformed packet is received:

1. Server may send Disconnect packet with reason
2. Server closes TCP connection
3. Client should attempt reconnection

Disconnect reasons:

• 0x01: Protocol error
• 0x02: Authentication failed
• 0x03: Network full
• 0x04: Kicked by host
• 0x05: Network closed