Network Protocol Guide

This document defines the binary communication protocol used between the R-Type Client and Server. It is designed to be lightweight, low-latency, and suitable for real-time UDP communication.

1. Protocol Overview

• Transport Layer: UDP (User Datagram Protocol).
• Encoding: Strict Binary format (Little-Endian byte order).
• Architecture: Client-Server (Authoritative Server).
• Port: Default is 4242.

Note: Unlike text-based protocols (HTTP/JSON), this protocol sends raw bytes directly from memory structures to minimize bandwidth usage and parsing overhead.

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2. Packet Structure

Every packet sent over the network shares a common Header, followed by a variable-length Body.

2.1. Header Layout (4 Bytes)

Offset	Field Name	Type	Description
0x00	OpCode	uint16_t	Identifies the type of command (see Section 3).
0x02	Length	uint16_t	The size (in bytes) of the following Payload.

2.2. Visual Representation

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|             OpCode            |             Length            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
|                       Variable Payload...                     |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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3. Command List (OpCodes)

The protocol distinguishes between commands sent by the Client (C->S) and updates sent by the Server (S->C).

OpCode	Name	Direction	Payload Size	Description
0x01	C_Login	C -> S	0 bytes	Request to join the game session.
0x02	S_LoginSuccess	S -> C	4 bytes	Acknowledge connection & assign Player ID.
0x03	C_Input	C -> S	2 bytes	Player movement/action inputs.
0x04	S_EntitySpawn	S -> C	14 bytes	Create a new entity (Player, Mob, Bullet).
0x05	S_EntityDestroy	S -> C	4 bytes	Remove an entity from the world.
0x06	S_EntityPosition	S -> C	12 bytes	Update position of a dynamic entity.
0x07	C_Shoot	C -> S	0 bytes	Player request to fire weapon.

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4. Payload Specifications

This section details the byte layout for the body of each command type.

4.1. C_Input (0x03)

Sent by the client every tick to update input state.

Offset	Type	Name	Description
0x00	int8_t	DirX	Horizontal axis (-1: Left, 1: Right, 0: None).
0x01	int8_t	DirY	Vertical axis (-1: Up, 1: Down, 0: None).

4.2. S_EntitySpawn (0x04)

Sent by the server when a new object enters the visual field.

Offset	Type	Name	Description
0x00	uint32_t	EntityID	Unique Network ID.
0x04	uint8_t	Type	0=Player, 1=Mob_Basic, 2=Bullet, 3=PowerUp.
0x05	float	PosX	Initial X Coordinate.
0x09	float	PosY	Initial Y Coordinate.
0x0D	uint8_t	Team	0=Ally, 1=Enemy (for collision logic).

4.3. S_EntityPosition (0x06)

High-frequency update to sync movements.

Offset	Type	Name	Description
0x00	uint32_t	EntityID	Unique Network ID.
0x04	float	X	New X Coordinate.
0x08	float	Y	New Y Coordinate.

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Authors

Epitech Paris

• Raphaël Chanliongco
• Hubert Touraine
• Jean-Baptiste Boshra
• Gabin Rudigoz
• Ylan Cuvier
• Swann Grandin

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