server.py

import socket
import threading

# Server constants
HOST = '0.0.0.0'
PORT = 5555
USERNAME_MAX_LENGTH = 30  # Maximum character limit for usernames

clients = {}  # Store connected clients with their usernames
users = []
server_version = 0.06

def broadcast(message, sender_client=None):
    """Send a message to all clients except the sender."""
    for client in clients:
        if client != sender_client:
            try:
                client.send(message)
            except:
                remove_client(client)

def handle_client(client):
    """Handle incoming messages from a client."""
    Recieving = False
    try:
        while not Recieving:
            # Listen for the initial ping request
            message = client.recv(1024).decode('utf-8')

            if message == "UML":
                # Send username character limit to the client UML == Username Max Length
                client.send(f"USERNAME_MAX_LENGTH:{USERNAME_MAX_LENGTH}".encode())

            elif message == "VERSION":
                # Send server version to client
                client.send(f"VERSION:{server_version}".encode())

            elif message == "GETUSERS":
                print("Sending users list")
                client.send(f"UserUpdate: {str(users)}".encode())

            elif message == "START":
                Recieving = True

        Recieving = False
        # Now, receive the username
        username = client.recv(1024).decode('utf-8').strip()

        # Validate username length
        if not username or len(username) > USERNAME_MAX_LENGTH or " " in username:
            client.send("ERROR: Username is invalid or too long.".encode())
            client.close()
            return

        # Register client with username
        clients[client] = username
        users.append(username)
        print(f"{username} joined the chat")
        broadcast(f"UserUpdate: {str(users)}".encode())

        # Notify others that a new user has joined
        broadcast(f"Server: {username} joined the chat.".encode())


        # Start message reception loop
        while True:
            encrypted_message = client.recv(1024)  # Receive the encrypted message
            if not encrypted_message:
                break
            broadcast(f"{username}: ".encode() + encrypted_message, sender_client=client)

    except Exception as e:
        print(f"Error handling client: {e}")
    finally:
        remove_client(client)

def remove_client(client):
    """Remove a client from the clients list and close the connection."""
    username = clients.pop(client, "Unknown")
    print(f"{username} left the chat")
    users.remove(username)
    broadcast(f"UserUpdate: {str(users)}".encode())
    broadcast(f"SERVER: {username} has left the chat.".encode())  # Notify others
    client.close()

def server():
    """Run the chat server."""
    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    server_socket.bind((HOST, PORT))
    server_socket.listen()
    print(f"Server started on {HOST}:{PORT}")

    while True:
        client, addr = server_socket.accept()
        threading.Thread(target=handle_client, args=(client,)).start()

if __name__ == "__main__":
    server()