📡 A protocol system in C++

Table of contents

• Repository
• Introduction
• Tech stack
• Architecture
  • PacketManager
    • Global functions
    • handlePacket(Packet &packet)
  • PacketHandler
    • ServerPacketHandler
    • ClientPacketHandler
  • Fields
    • Character field
    • Integer field (4 bytes)
    • Unsigned Integer field (4 bytes)
    • Unsigned Integer 64 field (8 bytes)
    • String field
  • Packets
    • CallUpPacket
    • HangUpPacket
    • ContactPacket
    • LoginErrorPacket
    • LoginPacket
    • LogoutPacket
    • MessagePacket
• Sample implementation
• Future ?

Repository

Introduction

During the realization of the Babel project, I had to work on a protocol system, to enable interactions between the client and the server.

If you want more details about the base project, feel free to click here.

Tech stack

• Programming language: C++

The protocol system does not depend on anything else.

Architecture

PacketManager

• Global functions

  • deserialize(std::string &packet)

    1. message[0] == '0x32'?
       We check if the first byte is our magic value.
    
    2. PacketType = message[1]
       We retrieve the packet type from the next byte.
    
    3. PacketField[] = message[2..]
       We convert the rest of the content into a list of packet field.
    
    4. Packet = Deserialize(PacketType, PacketField[])
       We call the deserialize function for the specific packet type, with the list of packet fields.
    

  • serialize(Packet&)

    It will simply call the serialize inherited function from the Packet class.

• handlePacket(Packet &packet)

  • Server-side implementation

  • Client-side implementation

  A trivial implementation of the handlePacket function is to simply loop through all PacketHandlers, to target the one registered for the received packet.

  You can also use a HashMap<PacketType, PacketHandler>.

PacketHandler

• ServerPacketHandler

  handle(Packet&, std::shared_ptr<ServerManager>, IoClient*)
  

• ClientPacketHandler

  handle(Packet&, std::shared_ptr<ClientManager>)
  

Fields

Here’s the base structure of a field

• Character field

• Integer field (4 bytes)

• Unsigned Integer field (4 bytes)

• Unsigned Integer 64 field (8 bytes)

• String field

Packets

Here’s the base structure of a packet:

• CallUpPacket

• HangUpPacket

• ContactPacket

• LoginErrorPacket

• LoginPacket

• LogoutPacket

• MessagePacket

Sample implementation

You can check out the GitHub wiki to have more details on an example implementation.

Future ?

If I ever get the time to work on my protocol system, I would definitely write a file parser to create packets from simple json files.

/cpp/ /server/ /communication/