client.py

import socket
import threading
import json
import sys

HOST = '127.0.0.1'
PORT = 9000

class Client:
    def __init__(self, name):
        self.name = name
        self.conn = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.conn.connect((HOST, PORT))
        print(f'{name} connected')
        threading.Thread(target=self.listen, daemon=True).start()

    def sub(self, topic):
        self.conn.send(json.dumps({
            'action': 'sub',
            'topic': topic
        }).encode())
        print(f'{self.name} subscribed to {topic}')

    def pub(self, topic, content):
        self.conn.send(json.dumps({
            'action': 'pub',
            'topic': topic,
            'content': content
        }).encode())
        print(f'{self.name} published: {content}')

    def listen(self):
        while True:
            try:
                data = self.conn.recv(4096).decode()
                if not data:
                    break
                msg = json.loads(data)
                print(f'\n[{self.name}] received "{msg["content"]}" on {msg["topic"]}')
                print(f'{self.name}> ', end='', flush=True)
            except:
                break

    def shell(self):
        print(f'Commands: sub TOPIC | pub TOPIC MSG | quit')
        while True:
            cmd = input(f'{self.name}> ').strip()
            if cmd == 'quit':
                break
            elif cmd.startswith('sub '):
                _, topic = cmd.split(' ', 1)
                self.sub(topic)
            elif cmd.startswith('pub '):
                parts = cmd.split(' ', 2)
                if len(parts) == 3:
                    _, topic, msg = parts
                    self.pub(topic, msg)
                else:
                    print('Usage: pub TOPIC MESSAGE')
            else:
                print('Use: sub TOPIC | pub TOPIC MSG | quit')
        self.conn.close()

if __name__ == '__main__':
    if len(sys.argv) < 2:
        print('Usage: python3 client.py NAME')
        sys.exit(1)
    c = Client(sys.argv[1])
    c.shell()