Python AWS iot SDK订阅

Question

订阅主题时我可能会遗漏一些东西但不确定.Below是我的iot python订阅代码，它完美无缺。但是，如果我运行没有订阅代码的代码“myAWSIoTMQTTClient.subscribe（”topic_1“，1，customCallback）”topic_1被发布但是如果尝试访问从python的另一个控制台订阅topic_1它只返回true并且不打印消息从自定义调用back.only如果保持订阅和发布在相同的python控制台它工作，但我尝试它运行订阅并在单独的控制台发布然后它抛出一个错误。换句话说，我如何订阅已创建的主题？

from AWSIoTPythonSDK.MQTTLib import AWSIoTMQTTClient
import time
import argparse
import json

host = "XXXXXXXX.iot.us-east-2.amazonaws.com"
rootCAPath = "root-CA.crt"
certificatePath = "XXXXX.cert.pem"
privateKeyPath = "XXXXX.private.key"
port = 8883
clientId = "sdk-java"
topic = "topic_1"
message_to_print="aws aws_preethi"

def customCallback(client, userdata, message):
    print("Received a new message: ")
    print(message.payload)
    print("from topic: ")
    print(message.topic)
    print("--------------\n\n")


myAWSIoTMQTTClient = AWSIoTMQTTClient(clientId)
myAWSIoTMQTTClient.configureEndpoint(host, port)
myAWSIoTMQTTClient.configureCredentials(rootCAPath, privateKeyPath, certificatePath)

# AWSIoTMQTTClient connection configuration
myAWSIoTMQTTClient.configureAutoReconnectBackoffTime(1, 32, 20)
myAWSIoTMQTTClient.configureOfflinePublishQueueing(-1)  # Infinite offline Publish queueing
myAWSIoTMQTTClient.configureDrainingFrequency(2)  # Draining: 2 Hz
myAWSIoTMQTTClient.configureConnectDisconnectTimeout(10)  # 10 sec
myAWSIoTMQTTClient.configureMQTTOperationTimeout(5)  # 5 sec

# Connect and subscribe to AWS IoT
myAWSIoTMQTTClient.connect()
myAWSIoTMQTTClient.subscribe("topic_1", 1, customCallback)

# Publish to the same topic in a loop forever
loopCount = 0
while True:
    message = {}
    message['message'] = message_to_print
    message['sequence'] = loopCount
    messageJson = json.dumps(message)
    myAWSIoTMQTTClient.publish(topic, messageJson, 1)
    loopCount += 1
    time.sleep(10)

Answer 1

我相信你需要为每个运行的脚本实例使用clientId的唯一值，否则第二个运行的实例将断开第一个实例的连接。

来自此论坛帖子：https://forums.aws.amazon.com/thread.jspa?threadID=219513

MQTT客户端ID与AWS IoT中的Thing没有关联。这些客户端ID纯粹是唯一标识MQTT连接。关于MQTT客户端ID需要考虑的一件重要事情是，它们需要在您的AWS账户中的设备之间保持唯一。如果您将客户端连接为“客户端ID 1”，并且第二个客户端使用相同的ID（“客户端ID 1”）连接，则第一个客户端的连接将被强制断开连接。这是MQTT规范的一项功能，可以使客户端产生间歇性连接，从而产生多个MQTT会话。

Answer 2

这样做如下：

# Connect and subscribe to AWS IoT
myAWSIoTMQTTClient.connect()

# Publish to the same topic in a loop forever
loopCount = 0
while True:
    myAWSIoTMQTTClient.subscribe("topic_1", 1, customCallback)
    message = {}
    message['message'] = message_to_print
    message['sequence'] = loopCount
    messageJson = json.dumps(message)
    myAWSIoTMQTTClient.publish(topic, messageJson, 1)
    loopCount += 1
    time.sleep(1)