python 3 paho mqtt发布/订阅的json消息将不解析

# -*- coding: utf-8 -*- import paho.mqtt.client as mqtt import json mqtt_broker = '192.168.1.111' mqtt_topic_one = 'mqtt_topic/tops_one' mqtt_topic_two = 'mqtt_topic/tops_two' json_data_1 = '''{ "this_json": "info", "data": { "multi_keyval": { "1": "1", "5": "5", "15": "15" }, "single_keyval": { "single_key": "200" } } }''' def pass_to_func_and_pub(data_to_pub): print(data_to_pub) # --------> This PRINTS print(json.loads(data_to_pub)) # --------> This DOES NOT PRINT # The following two lines don't work either. unpacked_json = json.loads(data_to_pub) client.publish(mqtt_topic_two, unpacked_json['this_json']) def on_connect(client, userdata, flags, rc): client.subscribe(mqtt_topic_one) client.publish(mqtt_topic_one, json_data_1) def on_message(client, userdata, msg): pass_to_func_and_pub(str(msg.payload)) client = mqtt.Client() client.on_connect = on_connect client.on_message = on_message client.connect(mqtt_broker) try: client.loop_forever() except KeyboardInterrupt: client.disconnect() print('MQTT client disconnected, exiting now.')

这里有几个问题。

1。异常处理

你没有处理异常(paho实际上在处理程序中忽略了它们,我想是为了让客户机保持活力)。这意味着当是投掷 json.loads(data_to_pub) ,您从未看到此消息,但函数已退出,因为没有本地 except 块。

改进版

def pass_to_func_and_pub(data_to_pub):
    print("Raw data: ", data_to_pub)
    try:
        unpacked_json = json.loads(data_to_pub)
    except Exception as e:
        print("Couldn't parse raw data: %s" % data_to_pub, e)
    else:
        print("JSON:", unpacked_json)
        client.publish(mqtt_topic_two, unpacked_json['this_json'])

等等,什么例外?

运行此改进版本,我们现在可以看到:

Couldn't parse raw data: b'{\n "this_json": "info",\n "data": {\n "multi_keyval": {\n "1": "1",\n "5": "5",\n "15": "15"\n },\n "single_keyval": {\n "single_key": "200"\n }\n }\n}' Expecting value: line 1 column 1 (char 0)

嗯,那是什么 b' 在那里干什么? …

2。编码问题

基本上你的问题归结为一条线

def on_message(client, userdata, msg):
    pass_to_func_and_pub(str(msg.payload))

通过呼叫 str 上 payload 其中 MqttMessage , 哪个是 bytes 对象 在Python3中,您将得到这些字节的字符串化版本,例如。 b'foobar' .

这个 b ,当然,现在使其无效的json,因此 Expecting value: line 1 column 1 (char 0) …

固定版本

不要打电话 STR ! Json.loads can handle bytes too . 所以:

def on_message(client, userdata, msg):
    pass_to_func_and_pub(msg.payload)

或者,假设使用utf-8编码,我们可以更明确地执行此操作(我更喜欢使用字符串):

def on_message(client, userdata, msg):
    pass_to_func_and_pub(msg.payload.decode('utf-8'))

希望能有帮助!