如何在 python 的 mqtt broker 上发布 json 数据？

Question

我正在尝试发布有关 MQTT 代理主题的 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 JSON 没有 payload={jsondata} 格式的数据，如何删除每次发布特定主题数据时出现的有效负载？

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" }]

Answer 1

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"}

你在其他地方有一个描述该有效载荷的操纵字符串将不需要的密钥添加到 msg

Answer 2

我对你的代码进行了一些修改，然后你可以将 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()

如何在 python 的 mqtt broker 上发布 json 数据？

How to publish json data on mqtt broker in python?

python

mqtt

paho