发送和接收消息的raspberry pi上的python mqtt脚本

Question

MQTT问题：

嗨，我正在尝试在多个覆盆子Pis（从两个开始）之间建立MQTT网络。 我有一个覆盆子pi（RPi-A），MQTT客户机，附带一个热敏电阻传感器，还有一个覆盆子（RPi-B），MQTT代理/客户机，作为我网络的中心。 通过python脚本，我希望温度每隔30分钟通过MQTT从RPi-A发送到主题传感器/数据，并由RPi-B接收。 当RPi-B通过topic sensor/data从RPi-a接收到消息时，我希望它通过MQTT topic sensor/instructions向RPi-a响应一条指令。 下面是我的脚本，到目前为止，RPi-A可以发送消息，RPi-B可以接收它们，但我无法计算RPi-B如何响应。

基本上，我试图理解的是，MQTT设备是否可以同时充当代理和客户机？ 而且，客户端可以同时发送和接收消息吗？如果可以，如何通过python实现上述所有功能？ 我读过很多博客、官方MQTT文章和paho模块文档（这对我来说很难理解），但仍然无法理解。谢谢你的帮助。

代码RPi-A（带热敏电阻传感器）：

from sense_hat import SenseHat
import time
import paho.mqtt.client as mqtt
import paho.mqtt.publish as publish
sense = SenseHat()

Broker = "192.168.1.252"

sub_topic = "sensor/instructions"    # receive messages on this topic

pub_topic = "sensor/data"       # send messages to this topic


############### sensehat inputs ##################

def read_temp():
    t = sense.get_temperature()
    t = round(t)
    return t

def read_humidity():
    h = sense.get_humidity()
    h = round(h)
    return h

def read_pressure():
    p = sense.get_pressure()
    p = round(p)
    return p

def display_sensehat(message):
    sense.show_message(message)
    time.sleep(10)

############### MQTT section ##################

# when connecting to mqtt do this;

def on_connect(client, userdata, flags, rc):
    print("Connected with result code "+str(rc))
    client.subscribe(sub_topic)

# when receiving a mqtt message do this;

def on_message(client, userdata, msg):
    message = str(msg.payload)
    print(msg.topic+" "+message)
    display_sensehat(message)

def publish_mqtt(sensor_data):
    mqttc = mqtt.Client("python_pub")
    mqttc.connect(Broker, 1883)
    mqttc.publish(pub_topic, sensor_data)
    #mqttc.loop(2) //timeout = 2s

def on_publish(mosq, obj, mid):
    print("mid: " + str(mid))


client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.connect(Broker, 1883, 60)


while True:
    sensor_data = [read_temp(), read_humidity(), read_pressure()]
    publish.single("monto/solar/sensors", str(sensor_data), hostname = Broker)
    time.sleep(1*60)

代码RPi-B（网络集线器）：

import time
import paho.mqtt.client as mqtt
import paho.mqtt.publish as publish

Broker = "192.168.1.252"

sub_topic = "sensor/data"    # receive messages on this topic

pub_topic = "sensor/instructions"               # send messages to this topic


# mqtt section

# when connecting to mqtt do this;

def on_connect(client, userdata, flags, rc):
    print("Connected with result code "+str(rc))
    client.subscribe(sub_topic)

# when receiving a mqtt message do this;

def on_message(client, userdata, msg):
    message = str(msg.payload)
    print(msg.topic+" "+message)
    publish_mqtt(‘got your message’)

# to send a message

def publish_mqtt(sensor_data):
    mqttc = mqtt.Client("monto_hub")
    mqttc.connect(Broker, 1883)
    mqttc.publish(pub_topic, "this is the master speaking")
    #mqttc.loop(2) //timeout = 2s

def on_publish(mosq, obj, mid):
    print("mid: " + str(mid))


client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.connect(Broker, 1883, 60)
client.loop_forever()

Answer 1

最简单的方法是使用client.loop_start()函数在单独的线程上启动网络循环，然后使用普通的client.publish方法

from sense_hat import SenseHat
import time
import paho.mqtt.client as mqtt
import paho.mqtt.publish as publish
sense = SenseHat()

Broker = "192.168.1.252"

sub_topic = "sensor/instructions"    # receive messages on this topic

pub_topic = "sensor/data"       # send messages to this topic


############### sensehat inputs ##################

def read_temp():
    t = sense.get_temperature()
    t = round(t)
    return t

def read_humidity():
    h = sense.get_humidity()
    h = round(h)
    return h

def read_pressure():
    p = sense.get_pressure()
    p = round(p)
    return p

def display_sensehat(message):
    sense.show_message(message)
    time.sleep(10)

############### MQTT section ##################

# when connecting to mqtt do this;

def on_connect(client, userdata, flags, rc):
    print("Connected with result code "+str(rc))
    client.subscribe(sub_topic)

# when receiving a mqtt message do this;

def on_message(client, userdata, msg):
    message = str(msg.payload)
    print(msg.topic+" "+message)
    display_sensehat(message)

def on_publish(mosq, obj, mid):
    print("mid: " + str(mid))


client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.connect(Broker, 1883, 60)
client.loop_start()

while True:
    sensor_data = [read_temp(), read_humidity(), read_pressure()]
    client.publish("monto/solar/sensors", str(sensor_data))
    time.sleep(1*60)