Event_Based_Server/server.py

import socket
import threading
import json
import time
import uuid

HOST = '127.0.0.1'
PORT = 65432

# Global dictionaries for event subscriptions, client IDs, and game state.
event_subscriptions = {}   # event_name -> list of client sockets
client_ids = {}            # conn -> client_id
client_states = {}         # conn -> {"client_id", "username", "x", "y", "keys"}
lock = threading.Lock()

MOVE_SPEED = 200  # pixels per second

def handle_client(conn, addr):
    client_id = str(uuid.uuid4())
    with lock:
        client_ids[conn] = client_id
        # Initialize state: default username "Guest", starting position, and an empty set of pressed keys.
        client_states[conn] = {"client_id": client_id, "username": "Guest", "x": 100, "y": 100, "keys": set()}
    print(f"[NEW CONNECTION] {addr} connected as {client_id}")
    
    # Send a dedicated "self_id" event so the client knows its unique id.
    try:
        msg = json.dumps({'event': 'self_id', 'payload': {'client_id': client_id}}) + "\n"
        conn.sendall(msg.encode())
    except Exception as e:
        print(f"[ERROR] sending self_id: {e}")
    
    # Broadcast that a new client connected.
    send_event("client_connect", {"client_id": client_id})
    
    try:
        file_obj = conn.makefile('r')
        for line in file_obj:
            line = line.strip()
            if not line:
                continue
            try:
                msg = json.loads(line)
                msg_type = msg.get('type')
                if msg_type == 'register_event':
                    event_name = msg.get('event')
                    with lock:
                        event_subscriptions.setdefault(event_name, []).append(conn)
                    print(f"[REGISTER] {client_id} subscribed to '{event_name}'")
                elif msg_type == 'set_username':
                    username = msg.get('username', 'Guest')
                    with lock:
                        if conn in client_states:
                            client_states[conn]['username'] = username
                    print(f"[USERNAME] {client_id} set username to '{username}'")
                elif msg_type == 'keydown':
                    key = msg.get('key')
                    with lock:
                        if conn in client_states:
                            client_states[conn]['keys'].add(key)
                    print(f"[KEYDOWN] {client_id} key '{key}' pressed")
                elif msg_type == 'keyup':
                    key = msg.get('key')
                    with lock:
                        if conn in client_states and key in client_states[conn]['keys']:
                            client_states[conn]['keys'].remove(key)
                    print(f"[KEYUP] {client_id} key '{key}' released")
                elif msg_type == 'ping':
                    # Respond immediately with a pong, echoing the timestamp.
                    timestamp = msg.get('timestamp')
                    response = json.dumps({'event': 'pong', 'payload': {'timestamp': timestamp}}) + "\n"
                    conn.sendall(response.encode())
                # Additional message types can be handled here.
            except json.JSONDecodeError:
                print(f"[ERROR] Invalid JSON from {client_id}: {line}")
    except Exception as e:
        print(f"[ERROR] Exception with {client_id}: {e}")
    finally:
        with lock:
            for subs in event_subscriptions.values():
                if conn in subs:
                    subs.remove(conn)
            client_ids.pop(conn, None)
            client_states.pop(conn, None)
        print(f"[DISCONNECT] {client_id} disconnected.")
        send_event("client_disconnect", {"client_id": client_id})
        conn.close()

def send_event(event_name, payload):
    """
    Broadcast an event to all clients subscribed to the given event.
    """
    message = json.dumps({'event': event_name, 'payload': payload}) + "\n"
    with lock:
        receivers = event_subscriptions.get(event_name, [])
        for client in receivers[:]:  # iterate over a copy to allow removals
            try:
                client.sendall(message.encode())
            except Exception as e:
                print(f"[ERROR] Failed to send to client, removing: {e}")
                receivers.remove(client)

def game_loop():
    """
    Main game loop: update each client’s position based on currently pressed keys,
    and broadcast the overall game state (including server time) to all clients.
    """
    dt = 0.1  #100 ms;

    while True:
        time.sleep(dt)
        with lock:
            # Update each client's position.
            for state in client_states.values():
                dx, dy = 0, 0
                if 'left' in state['keys']:
                    dx -= MOVE_SPEED * dt
                if 'right' in state['keys']:
                    dx += MOVE_SPEED * dt
                if 'up' in state['keys']:
                    dy -= MOVE_SPEED * dt
                if 'down' in state['keys']:
                    dy += MOVE_SPEED * dt
                state['x'] += dx
                state['y'] += dy
            # Build payload: include current server time and each client’s state.
            players_payload = {}
            for state in client_states.values():
                players_payload[state['client_id']] = {
                    "username": state['username'],
                    "x": state['x'],
                    "y": state['y']
                }
            payload = {"server_time": time.time(), "players": players_payload}
        send_event("state_update", payload)

def start_server():
    print("[STARTING] Server is starting...")
    threading.Thread(target=game_loop, daemon=True).start()
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
        s.bind((HOST, PORT))
        s.listen()
        print(f"[LISTENING] Server is listening on {HOST}:{PORT}")
        while True:
            conn, addr = s.accept()
            threading.Thread(target=handle_client, args=(conn, addr), daemon=True).start()

if __name__ == "__main__":
    start_server()