树莓派上的python mqtt脚本发送和接收消息

问题描述

MQTT问题:

您好，我正在尝试在多个Raspberry Pi(以两个开头)之间建立MQTT网络.我有一个树莓派(RPi-A)，MQTT客户端和一个热敏电阻传感器，还有一个树莓派(RPi-B)，MQTT代理/客户端，充当我的网络的集线器.通过python脚本，我希望温度每30分钟从RPi-A通过MQTT发送到主题传感器/数据，并由RPi-B接收.当RPi-B通过主题传感器/数据从RPi-A接收到消息时，我希望它通过MQTT主题传感器/指令向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，而RPi-B可以接收消息，但是我无法确定RPi-B的响应方式.

Hi, I’m trying to set up a MQTT network between multiple Raspberry Pis (starting with two).I have one raspberry pi (RPi-A), MQTT client, with a thermistor sensor attached and one raspberry (RPi-B), MQTT broker/client, acting as a hub for my network.Through python scripting I’d like the temperature to be sent every 30mins from RPi-A via MQTT to topic sensor/data and received by RPi-B.When RPi-B receives a message from RPi-A via topic sensor/data, I want it to respond with an instruction via MQTT topic sensor/instructions to RPi-A.Below is my script, so far RPi-A can send messages and RPi-B receive them but I cannot work out how RPi-B can respond.

基本上，我想了解的是，MQTT设备能否同时充当代理和客户端?并且，客户端可以发送和接收消息吗?如果可以，那么如何通过python实现以上所有功能?我已经阅读了很多博客，MQTT官方文章和paho模块文档(对我来说很难理解)，但是仍然无法解决.您的帮助将是最有用/最感激的.

Basically, what I’m trying to understand is, is it possible for a MQTT device to act as both broker and client at the same time?And, can a client both send and receive messages and if so how to implement all the above via python?I’ve read a lot of blogs, official MQTT articles and the paho module documentation (which for me is very hard to fathom) but still cannot figure this out. Your help would be most useful/ appreciated.

代码RPi-A(带有热敏电阻传感器):

Code RPi-A ( with thermistor sensor):

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):

Code RPi-B (network hub):

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()

推荐答案

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，然后使用常规的client.publish方法

The simplest way is to start the network loop on a separate thread using the client.loop_start() function, then use the normal client.publish method

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)

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