在不订阅python Paho MQTT库的情况下接收消息

import socket

# MQTT broker的IP地址和端口号
broker_ip = 'broker.example.com'
broker_port = 1883

# MQTT连接报文
connect_packet = b'\x10\x12\x00\x04MQTT\x04\x02\x00\x3c\x00\x0a\x00\x08my_client'

# 创建TCP套接字并连接到MQTT broker
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((broker_ip, broker_port))

# 发送连接报文
sock.send(connect_packet)

# 接收并解析返回的CONNACK报文
connack_packet = sock.recv(1024)
if connack_packet[0] == 0x20 and connack_packet[1] == 0x02 and connack_packet[3] == 0x00:
    print('Connected to MQTT broker')

# 循环接收并处理消息
while True:
    # 接收消息报文
    msg_packet = sock.recv(1024)

    # 解析消息报文
    msg_type = (msg_packet[0] & 0xf0) >> 4
    if msg_type == 3:  # 如果是PUBLISH消息
        topic_len = (msg_packet[2] << 8) + msg_packet[3]
        topic = msg_packet[4:4+topic_len].decode('utf-8')
        payload = msg_packet[4+topic_len:]

        # 处理接收到的消息
        print(f'Received message on topic "{topic}": {payload.decode("utf-8")}')

# 关闭套接字
sock.close()