How to detect when MQTT client disconnects from AWS IoT MQTT Broker?

Question

I'm working on a small router that connects via LTE/3G to an AWS IoT MQTT Broker to publish messages on a regular basis. When internet is working and the router's AWSIoTMQTTClient could connect to the broker, messages are sent and everything works fine.

But when the device lose internet connection, I want to store the messages that should have been sent while the device was offline on local disk. As soon as connection to AWS is possible, then continue sending to the broker and do not save on disk.

On my test so far, the onOnline and onOffline functions have not worked correctly when I disconnect the internet.

When I start my test with internet connection, the "on_online" function gets called and messages are being sent. While the device is working and sending messages, I turn off the internet but the "on_offline" functions never gets called. So all messages will be transferred to the broker as soon as internet/connection to AWS works again. (Because I set my client to "Infinite offline Publish queueing").

When I start my test without internet connection, the "on_offline" functionnever gets called.

from AWSIoTPythonSDK.MQTTLib import AWSIoTMQTTClient
from time import time

def on_online():
  global awsClient_Online
  awsClient_Online = True

def on_offline():
  global awsClient_Online
  global awsClient_OfflineSince
  awsClient_Online = False
  awsClient_OfflineSince = time()

def main():
  # Init AWSIoTMQTTClient
  awsClient = None
  awsClient = AWSIoTMQTTClient(Aws_ClientId)
  awsClient.configureEndpoint(Aws_ApiEndpoint, Aws_Port)
  awsClient.configureCredentials(Aws_RootCa, Aws_PrivateKey, Aws_CertFile)

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

  # Register a onOnline/onOffline callback
  awsClient.onOnline = on_online
  awsClient.onOffline = on_offline

  global awsClient_Online
  global awsClient_OfflineSince
  # Connect to AWS IoT
  try:
    awsClient.connect()
    '''
    According to documentation should return True when connection OK,
    False when not OK.. but I'm getting error "socket.gaierror: [Errno -3] 
    Temporary failure in name resolution" when no internet
    https://s3.amazonaws.com/aws-iot-device-sdk-python-docs/html/index.html#AWSIoTPythonSDK.MQTTLib.AWSIoTMQTTClient.connect
    '''
  except:
    awsClient_Online = False
    awsClient_OfflineSince = time()

  # Cyclic program
  while True:
    if not awsClient_Online:
      try:
        awsClient.connect()
      except:
        awsClient_Online = False
        awsClient_OfflineSince = time()

    if awsClient_Online:
      # Send messages
    else:
      # Save on disk

I thought the variable "awsClient._mqtt_core._client_status._status" would update whenever the connection was lost/back again, but it does not. For instance when it is "4" (connected, as long I've seen) and then I disconnect the internet, it remains on "4".

How can I effectively know when the connection to AWS failed?

How to detect when MQTT client disconnects from AWS IoT MQTT Broker?

0 Answers0