mqtt 组成

1、mqtt 服务器 2、mqtt 订阅者 sub 3、mqtt 发送者 pub

搭建mqtt  使用emqx，我的本地机器是centos 8 云服务是 centos 7.8，搭建大同小异

搭建服务的话，看官网最好  

https://docs.emqx.cn/cn/broker/latest/getting-started/install.html#shell-%E8%84%9A%E6%9C%AC%E4%B8%80%E9%94%AE%E5%AE%89%E8%A3%85-linux

然后就是测试啥的了，用python 测试 订阅 发送

先写订阅 建立 sub_car.py

class MqttSub(object):
    def __init__(self, topic):
        self.client = mqtt.Client()
        self.topic = topic
        self.username = 'caoyong'
        self.password = 'admin123'

    def on_connect(self, client_driver, userdata, flags, rc):
        logger.info("Connected with result code: " + str(rc))
        print("Connected with result code: " + str(rc))
        print(rc)
        if rc == 0:
            client_driver.subscribe(self.topic, qos=0)

    @classmethod
    def on_message(cls, client_driver, userdata, msg):
        logger.info(f'{msg.topic} {msg.payload}')
        print(f'{msg.topic} {msg.payload}')
        sub_data = json.loads(msg.payload.decode('utf-8'))
        logger.info(f'{get_now()}{sub_data}')
        print(sub_data)
        start_time = sub_data['time']
        end_time = time.time() - start_time
        print('消息从发送到接收的时间', end_time)
        logger.info(f'{get_now()}消息从发送到接收的时间{end_time}')

        if 'open_door' in sub_data.keys():
            open_door()

        end_time = time.time() - start_time
        print(end_time)
        logger.info(f'{get_now()}最终时间{end_time}')

    def mqtt_main(self):
        self.client.username_pw_set(username=self.username, password=self.password)
        self.client.connect('192.168.22.70', 61883, 600)
        self.client.on_connect = self.on_connect
        self.client.on_message = self.on_message
        self.client.loop_forever(retry_first_connection=True)  # 保持连接



if __name__ == '__main__':
    now_topic = 'door'
    MqttSub(topic=now_topic).mqtt_main()

然后 发布  pub_car.py

import json
import time

import paho.mqtt.client as mqtt


if __name__ == '__main__':
    control_topic = 'control'
    client = mqtt.Client()
    client.username_pw_set(username='caoyong', password='admin123')
    client.connect('192.168.22.70', 61883, 600)  # 600为keepalive的时间间隔
    push_new = {'0': 1, 'time': time.time(),
                'push_rtmp': 0,
                'camera_up_down': {'angle': 45},
                'camera_left_right': {'angle': 90},
                'car_left_right': {'angle': 45},
                'car_up_down': {'car_status': 1, 'speed': 'high'},
                'cat_stop': 1
                }

    client.publish(control_topic, payload=json.dumps(push_new), qos=0)

然后发现一个问题，mqtt 使用本地电脑 查看时间 要 0.015s  使用其他电脑 订阅  居然要 2s+ 不知道为啥，计划用mqtt 控制，但是 实际操作起来 不太可行 延迟太大