Question

我正在使用带有paho-mqtt的Python客户端在Google Cloud IoT的这个特定主题中发布：projects/my_project/topics/sm1。我的代码如下，基于Google IoT文档的示例：

import paho.mqtt.client as mqtt
import ssl, random, jwt_maker
from time import sleep

root_ca = './../roots.pem'
public_crt = './../my_cert.pem'
private_key = './../my_pr.pem'

mqtt_url = "mqtt.googleapis.com"
mqtt_port = 8883
mqtt_topic = "/projects/my_project/topics/sm1"
project_id   = "my_project"
cloud_region = "us-central1"
registry_id  = "sm1"
device_id    = "sm1"

connflag = False

def error_str(rc):
    """Convert a Paho error to a human readable string."""
    return "Some error occurred. {}: {}".format(rc, mqtt.error_string(rc))

def on_disconnect(unused_client, unused_userdata, rc):
    """Paho callback for when a device disconnects."""
    print("on_disconnect", error_str(rc))

def on_connect(client, userdata, flags, response_code):
    global connflag
    connflag = True
    print("Connected with status: {0}".format(response_code))

def on_publish(client, userdata, mid):
    print("User data: {0} -- mid: {1}".format(userdata, mid))
    #client.disconnect()

if __name__ == "__main__":

    client = mqtt.Client("projects/{}/locations/{}/registries/{}/devices/{}".format(
                         project_id,
                         cloud_region,
                         registry_id,
                         device_id))

    client.username_pw_set(username='unused',
                           password=jwt_maker.create_jwt(project_id,
                                               private_key,
                                               algorithm="RS256"))

    client.tls_set(root_ca,
                   certfile = public_crt,
                   keyfile = private_key,
                   cert_reqs = ssl.CERT_REQUIRED,
                   tls_version = ssl.PROTOCOL_TLSv1_2,
                   ciphers = None)

    client.on_connect = on_connect
    client.on_publish = on_publish
    client.on_disconnect = on_disconnect

    print("Connecting to Google IoT Broker...")
    client.connect(mqtt_url, mqtt_port, keepalive=60)
    client.loop_start() 

    while True:
        sleep(0.5)
        print connflag
        if connflag == True:
            print("Publishing...")
            ap_measurement = random.uniform(25.0, 150.0)
            #payload = "sm1/sm1-payload-{}".format(ap_measurement)
            res = client.publish(mqtt_topic, ap_measurement, qos=1)
            if not res.is_published():
               print("Data not published!!")
            else:
               print("ActivePower published: %.2f" % ap_measurement)
        else:
            print("Waiting for connection...")

当我运行时，客户端连接但不发布。在Google IoT控制台，我可以看到以下错误消息：

无效的MQTT发布主题：projects / my_project / topics / sm1

这是输出：

连接到Google IoT Broker ...
  已连接状态：0 - msg：已接受连接。
  真
  出版...
  数据未公布!!
  （＆＃39; on_disconnect＆＃39;，＆＃39;发生了一些错误.1：内存不足。＆＃39;）

这真的很奇怪，因为主题在那里，创建并与之相关联！

任何帮助将不胜感激。我已经阅读了以下文档和代码：

Answer 1

您的主题名称不正确。

令人困惑（我也只是打了它）。

客户端ID（如您所示）必须是：

"projects/{}/locations/{}/registries/{}/devices/{}".format(
  project_id,
  cloud_region,
  registry_id,
  device_id
)

主题必须是以下形式：

/devices/{}/config
/devices/{}/state
/devices/{}/events
/devices/{}/events/some/other/topic

正如@ptone的评论所述：

在cloud iot核心中，MQTT主题与Cloud PubSub主题是多对一的。对于安全性 - 设备可能只发布前缀为其设备名称空间的MQTT主题。然后，您可以匹配sub-topics to other Cloud PubSub topics as noted here，但最多只匹配10.这不是为了允许1：1映射设备到PubSub主题。

希望有所帮助！

Answer 2

当我将mqtt_topic从events更改为state时，我的python代码正常工作。在此示例中，我尝试将当前温度和湿度从我的设备上传到Google IoT Core。

  ...
  data =  {'temp': temperature, 'humid': humidity}
  device_id = 'freedgePrototype'
  topic = 'state'

  mqtt_topic = '/devices/{}/{}'.format(device_id, topic)
  payload = json.dumps(data)
  print('Publishing message  {}'.format(payload))

  client.publish(mqtt_topic, payload, qos=1)

结果看起来像这样。

Google Cloud IoT - 无效的MQTT发布主题

2 个答案: