python mqtt 订阅多条消息答案

【问题标题】：python mqtt subscribe to mutliple messagepython mqtt 订阅多条消息
【发布时间】：2020-09-10 11:23:22
【问题描述】：

我确实发布了多条消息：

#!/usr/bin/env python3

import paho.mqtt.publish as publish

topic1 = "testtopic/topic1"
topic2 = "testtopic/topic2"

val1 = b'54.8'
val2 = b'598.45'
val3 = b'4813.9'

msgs = [(topic1, val1),
        (topic1, val2),
        (topic2, val3)]

publish.multiple(msgs, hostname="localhost")

订阅时

#!/usr/bin/env python3

import paho.mqtt.client as mqtt
import json

broker_url = "localhost"
broker_port = 1883

def on_connect(client, userdata, flags, rc):
    print("Connected With Result Code: {}".format(rc))
def on_disconnect(client, userdata, rc):
    print("Client Got Disconnected")
def on_message(client, userdata, message):
    msg = json.loads(message.payload.decode())
    print("Message Recieved: " + str(msg))
    
client = mqtt.Client()
client.connect(broker_url, broker_port)

client.on_connect = on_connect
client.on_message = on_message
client.on_disconnect = on_disconnect

topic = "testtopic/#"

client.subscribe(topic, qos=0)

client.loop_forever()

我明白了

Connected With Result Code: 0
Message Recieved: 54.8
Message Recieved: 598.45
Message Recieved: 4813.9

如何将这三个值分配给单个变量（例如 value1 = 54.8、value2 = 598.45、value3 = 598.45），以便能够像进行一些计算或将其保存到文件一样使用它们。

【问题讨论】：

也许每次收到消息时，将其附加到列表中？
您可以在 JSON 中发布值，例如 {"value1": 54.8, "value2": 598.45, "value3": 598.45}

标签： python mqtt publish-subscribe

【解决方案1】：

你可以像下面这样使用 JSON 格式..

#!/usr/bin/env python3
import paho.mqtt.publish as publish

topic1 = "testtopic/topic1"
topic2 = "testtopic/topic2"

val1 = b'54.8'
val2 = b'598.45'
val3 = b'4813.9'

payload1=json.dumps({"value1":val1, "value2":val2})
payload2=json.dumps({"value3":val3)

msgs = [(topic1, payload1),
        (topic2, payload2)]

publish.multiple(msgs, hostname="localhost")

对于 on_message 函数中的订阅者...

def on_message(client, userdata, message):
    msg = json.loads(message.payload.decode())
    res=json.loads(str(msg))
    if message.topic == topic1:
           print(str(res["value1"])+" & "+str(res["value2"]))
    else:
           print(str(res["value2"]))

【讨论】：