如何在 python 中在 mqtt 代理上发布 json 数据？答案

【问题标题】：How to publish json data on mqtt broker in python?如何在 python 中在 mqtt 代理上发布 json 数据？
【发布时间】：2017-03-11 06:11:18
【问题描述】：

我正在尝试在 MQTT 代理主题上发布 JSON 数据。这是源代码，我试过了-

import paho.mqtt.client as mqtt
import json
# Define Variables
MQTT_HOST = "localhost"
MQTT_PORT = 1883
MQTT_KEEPALIVE_INTERVAL = 45
MQTT_TOPIC = "irisPayload"

MQTT_MSG=json.dumps({"sepalLength": "6.4","sepalWidth":  "3.2","petalLength": "4.5","petalWidth":  "1.5"});
# Define on_publish event function
def on_publish(client, userdata, mid):
    print "Message Published..."
# Initiate MQTT Client
mqttc = mqtt.Client()

# Register publish callback function
mqttc.on_publish = on_publish

# Connect with MQTT Broker
mqttc.connect(MQTT_HOST, MQTT_PORT, MQTT_KEEPALIVE_INTERVAL)        

# Publish message to MQTT Broker    
mqttc.publish(MQTT_TOPIC,MQTT_MSG)

# Disconnect from MQTT_Broker
mqttc.disconnect()

我只想发布不带 payload={jsondata} 格式的 JSON 数据，当我发布特定主题的数据时，如何删除每次收到的有效负载？

在日志中它显示这样的消息--- [payload={ "sepalLength": "6.4", "sepalWidth": "3.2", "petalLength": "4.5", "petalWidth": "1.5" } ]

【问题讨论】：

您在哪里遇到了 'payload={jsondata}format' 的数据？
在日志中它显示我的数据为 payload={"sepalLength": "6.4","sepalWidth": "3.2","petalLength": "4.5","petalWidth": "1.5 "}.
我很确定“问题”出在您设置的代理方面以及您的代理的正常行为（无论您使用哪个）

标签： python mqtt paho

【解决方案1】：

我为您的代码添加了一些修改，然后您可以将 json 发布为字符串，然后接收字符串并转换为 json。

示例代码：

import paho.mqtt.client as mqtt
import json
# Define Variables
MQTT_HOST = "localhost"
MQTT_PORT = 1883
MQTT_KEEPALIVE_INTERVAL = 45
MQTT_TOPIC = "irisPayload"

MQTT_MSG=json.dumps({"sepalLength": "6.4","sepalWidth":  "3.2","petalLength": "4.5","petalWidth":  "1.5"});
# Define on_publish event function
def on_publish(client, userdata, mid):
    print "Message Published..."

def on_connect(client, userdata, flags, rc):
    client.subscribe(MQTT_TOPIC)
    client.publish(MQTT_TOPIC, MQTT_MSG)

def on_message(client, userdata, msg):
    print(msg.topic)
    print(msg.payload) # <- do you mean this payload = {...} ?
    payload = json.loads(msg.payload) # you can use json.loads to convert string to json
    print(payload['sepalWidth']) # then you can check the value
    client.disconnect() # Got message then disconnect

# Initiate MQTT Client
mqttc = mqtt.Client()

# Register publish callback function
mqttc.on_publish = on_publish
mqttc.on_connect = on_connect
mqttc.on_message = on_message

# Connect with MQTT Broker
mqttc.connect(MQTT_HOST, MQTT_PORT, MQTT_KEEPALIVE_INTERVAL)

# Loop forever
mqttc.loop_forever()

【讨论】：

【解决方案2】：

data = {"sepalLength": "6.4","sepalWidth":  "3.2","petalLength": "4.5","petalWidth":  "1.5"}
print json.dumps(data)

打印：

{"sepalLength": "6.4","sepalWidth": "3.2","petalLength": "4.5","petalWidth": "1.5"}

不是：

payload={"sepalLength": "6.4","sepalWidth": "3.2","petalLength": "4.5","petalWidth": "1.5"}

您在其他地方有一个描述该有效负载的操纵字符串将不需要的密钥添加到消息中

【讨论】：

@Asoul，是的，我正在谈论这个。 print(msg.payload) #