Server

When communicating via TCP, before sending a message whose length was unknown to the other side of the communication, I sent the length of the upcoming message. To implement the server, I opened two sockets - one TCP and one UDP - to receive messages from TCP and UDP clients respectively.

TCP Message Handling When receiving a message on the TCP socket (client connection attempt):

• Check if a client with a similar ID is already connected

• If exists: Send confirmation to client → client displays corresponding message

• If new: Add client to the vector of connected clients

UDP Message Handling

When receiving UDP messages:

• Translate/forward the message to corresponding TCP clients subscribed to the message's topic

TCP Client Management

When receiving messages from TCP clients on their connection socket:

• Handle subscribe/unsubscribe requests by adding/removing topics in the client's topic vector

• On client disconnect:

  • Mark as disconnected

  • Close socket fd

  • Keep in subscriber vector for potential reconnections

Client

The client communicates with the server through a TCP socket.

Connection Flow

• Sends desired connection ID to server

• Waits for server confirmation

Post-Connection

After successful connection:

• Can send subscribe/unsubscribe requests to server

• Waits for operation confirmation

Key implementation detail: All message lengths are pre-sent before actual content transmission to handle variable-length messages.