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📡 R-Type Network Protocol (Binary Edition)

📋 Overview

This document defines the Binary Protocol used for Client-Server communication in the R-Type Clone. It relies on UDP for transport and MsgPack for efficient data serialization.

Feature Specification
Transport UDP (via ASIO)
Serialization MsgPack (Binary)
Architecture Server-Authoritative
Update Rate 20Hz (50ms)

🛠 Internal Message Layout

Messages travelling through the engine's internal ZeroMQ bus use a specific binary packing to avoid string parsing overhead and corruption.

[ Topic Length (4 bytes) ] [ Topic String (N bytes) ] [ MsgPack Payload (M bytes) ]

📨 Core Messages

1. INPUT (Client ➔ Server)

Sent whenever a key is pressed or released.

Topic: INPUT
Payload (MsgPack Map):

Key Type Description
k String Key name (UP, DOWN, LEFT, RIGHT, SPACE)
s Integer State: 1 (Pressed), 0 (Released)

Lua Example:

ECS.sendBinary("INPUT", {k="UP", s=1})

2. ENTITY_POS (Server ➔ Clients)

Authoritative state broadcast for every moving entity.

Topic: ENTITY_POS
Payload (MsgPack Map):

Key Type Description
id String Unique Entity UUID
x, y, z Float World Position
rx, ry, rz Float World Rotation (Degrees)
vx, vy, vz Float Velocity (for Client Extrapolation)
t Integer Entity Type (1:Player, 2:Bullet, 3:Enemy)

3. PLAYER_ASSIGN (Server ➔ Client)

Assigns a unique ID and entity to a newly connected client.

Topic: PLAYER_ASSIGN
Payload: String (Entity ID)

🔄 Sequence Diagram

sequence_diagram
  Client ->> Server: RequestNetworkConnect
  Server -->> Client: NetworkStatus ("Connected")
  Server ->> Server: Create Player Entity
  Server -->> Client: PLAYER_ASSIGN (UUID)
  Client ->> Server: CLIENT_READY
  loop Gameplay
    Client ->> Server: INPUT (Binary MsgPack)
    Server ->> Server: Simulate Physics
    Server -->> Client: ENTITY_POS (Binary MsgPack)
    Client ->> Client: Interpolate & Render
  end
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🚀 Performance Benefits

  1. Zero Parsing: No string.match or stringstream needed.
  2. Compactness: MsgPack reduces payload size by ~40% compared to JSON/Text.
  3. Safety: Length-prefixed topics prevent buffer overflows and injection attacks.