Monitor AWS IoT connections in near-real time using MQTT LWT

In a linked gadget, you may need to observe devices in near-real time to detect error and mitigate actions, Last Will and Testament (LWT) methodology for MQTT addresses this drawback. LWT is an everyday methodology of MQTT protocol specification that allows to detect abrupt disconnects of devices and to tell totally different purchasers about this abrupt disconnections.

IoT devices are typically utilized in environments with unreliable neighborhood connectivity and/or devices might disconnect on account of lack of vitality present, low battery, lack of connection, or each different trigger. This may occasionally set off abrupt disconnections from the vendor with out determining if the disruption was pressured by the consumer or really abrupt, That’s the place LWT let’s a consumer current a testament along with its credentials when connecting to the AWS IoT Core. If the consumer disconnects abruptly in some unspecified time sooner or later later (i.e. vitality loss), it may let AWS IoT Core ship a message to totally different purchasers and inform them of this abrupt disconnect and ship LWT message.

MQTT Mannequin 3.1.1 provides an LWT attribute as part of the MQTT message and is supported by AWS IoT Core, so any shopper which disconnects abruptly can specify its LWT message along with the MQTT matter when it connects to the vendor. When the consumer disconnects abruptly, the vendor (AWS IoT Core) will then publish the LWT message supplied by that shopper at connection time to all the devices which subscribed to this LWT matter.

The MQTT LWT attribute means that you can monitor AWS IoT connections in near-real time that may help you to take corrective actions. You presumably can react to abrupt disconnection events by verifying standing, restoring connections, and ending up each edge-based (gadget side) actions or cloud-based actions to research and mitigate this abrupt disconnect of the gadget.

On this weblog we’ll endure following steps:

  1. A simulated ‘lwtThing’ gadget connects to AWS IoT Core by giving Protect-alive time
  2. The ‘lwtThing’ gadget, on the connection to AWS IoT Core, provides the following:
    1. Topic for LWT (i.e. /remaining/will/matter)
    2. LWT message
    3. QoS type each 0 or 1
  3. ‘lwtThing’ gadget disconnects abruptly from AWS IoT Core
  4. AWS IoT Core detects this and publishes the LWT message to all the subscribers of the topic (i.e. /remaining/will/matter)
  5. Tips for AWS IoT (rule engine) picks up the set off on the topic and invokes Amazon Straightforward Notifications Service (SNS)
  6. Amazon SNS sends a notification e-mail

We’ll setup a digital environment using a CloudFormation template (by using AWS IoT workshop setup instructions) and launch a digital IoT issue (naming ‘lwtThing’) to create an precise life simulation of the bodily gadget.


We’ll simulate the sting gadget using a script supplied beneath and ship the LWT message, displaying abrupt disconnects and triggering AWS IoT tips and subsequently invoking Amazon SNS to ship emails.


We’ll use the following workshop setup to get quickly bootstrapped and examine LWT. You must use the following hyperlink to setup AWS Cloud9 environment (select any space closest to your location).

As quickly as we’ve bought the environment setup using the workshop AWS CloudFormation pre-provided template, lets begin testing the ungraceful disconnects with AWS IoT Core (AWS MQTT vendor on the cloud).

Now open the Cloud9 terminal (see proper right here) and let’s setup Python SDK for us to utilize.

Create a folder for us to utilize to connect our IoT issue using the Cloud9 terminal window.

mkdir -p /dwelling/ubuntu/environment/lwt/certs
cd /dwelling/ubuntu/environment/lwt/

Setup Python IoT SDK using full instructions proper right here.

Quick instructions:

git clone
cd aws-iot-device-sdk-python
python arrange

Now, to setup your AWS IoT Issue adjust to steps outlined proper right here.

As quickly as we’ve bought created the issue, let’s add these certificates in our Cloud9 event for us to connect from there.

Add the newly created certificates and RootCA into following folder (created earlier)


LWT issue messages

Let’s copy the Python code to Cloud9 and execute as a result of the simulated AWS IoT issue.

Copy the following directions:


Open the file and reproduction the following code into it.

 * # Copyright, Inc. or its associates. All Rights Reserved.
 * # SPDX-License-Identifier: MIT-0

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

AllowedActions = ['both', 'publish', 'subscribe']

# Personalized MQTT message callback
def customCallback(shopper, userdata, message):
    print("Acquired a model new message: ")
    print("from matter: ")

# LWT JSON payload
payload ={
  "state": {
    "reported": {
      "last_will": "certain",
      "trigger_action": "on",
      "client_id": "lwtThing"
# conversion to JSON accomplished by dumps() carry out
jsonPayload = json.dumps(payload)
# printing the output

# Study in command-line parameters
parser = argparse.ArgumentParser()
parser.add_argument("-e", "--endpoint", movement="retailer", required=True, dest="host", help="Your AWS IoT personalized endpoint")
parser.add_argument("-r", "--rootCA", movement="retailer", required=True, dest="rootCAPath", help="Root CA file path")
parser.add_argument("-c", "--cert", movement="retailer", dest="certificatePath", help="Certificates file path")
parser.add_argument("-k", "--key", movement="retailer", dest="privateKeyPath", help="Private key file path")
parser.add_argument("-p", "--port", movement="retailer", dest="port", type=int, help="Port amount override")
parser.add_argument("-w", "--websocket", movement="store_true", dest="useWebsocket", default=False,
                    help="Use MQTT over WebSocket")
parser.add_argument("-id", "--clientId", movement="retailer", dest="clientId", default="basicPubSub",
                    help="Targeted shopper id")
parser.add_argument("-t", "--topic", movement="retailer", dest="matter", default="sdk/examine/Python", help="Targeted matter")
parser.add_argument("-m", "--mode", movement="retailer", dest="mode", default="every",
                    help="Operation modes: %s"%str(AllowedActions))
parser.add_argument("-M", "--message", movement="retailer", dest="message", default="AWS IoT Issue linked message to IoT Core",
                    help="Message to publish")

args = parser.parse_args()
host =
rootCAPath = args.rootCAPath
certificatePath = args.certificatePath
privateKeyPath = args.privateKeyPath
port = args.port
useWebsocket = args.useWebsocket
clientId = args.clientId
matter = args.matter

if args.mode not in AllowedActions:
    parser.error("Unknown --mode chance %s. Must be thought-about one among %s" % (args.mode, str(AllowedActions)))

if args.useWebsocket and args.certificatePath and args.privateKeyPath:
    parser.error("X.509 cert authentication and WebSocket are mutual distinctive. Please select one.")

if not args.useWebsocket and (not args.certificatePath or not args.privateKeyPath):
    parser.error("Missing credentials for authentication.")

# Port defaults
if args.useWebsocket and by no means args.port:  # When no port override for WebSocket, default to 443
    port = 443
if not args.useWebsocket and by no means args.port:  # When no port override for non-WebSocket, default to 8883
    port = 8883

# Configure logging - we'll see messages on STDOUT
logger = logging.getLogger("AWSIoTPythonSDK.core")
streamHandler = logging.StreamHandler()
formatter = logging.Formatter('%(asctime)s - %(establish)s - %(levelname)s - %(message)s')

# Init AWSIoTMQTTClient
myAWSIoTMQTTClient = None
if useWebsocket:
    myAWSIoTMQTTClient = AWSIoTMQTTClient(clientId, useWebsocket=True)
    myAWSIoTMQTTClient.configureEndpoint(host, port)
    myAWSIoTMQTTClient = AWSIoTMQTTClient(clientId)
    myAWSIoTMQTTClient.configureEndpoint(host, port)
    myAWSIoTMQTTClient.configureCredentials(rootCAPath, privateKeyPath, certificatePath)

# Will Topic
# Enter parameters are: Topic, Last will message and ultimately QoS
myAWSIoTMQTTClient.configureLastWill('/remaining/will/matter', jsonPayload, 0)

# Be part of and subscribe to AWS IoT
# keep-alive be part of parameter - setting 30s part of(30) 
loopCount = 1
whereas loopCount < 2:
    if args.mode == 'every' or args.mode == 'publish':
        message = {}
        message['message'] = args.message
        messageJson = json.dumps(message)
        myAWSIoTMQTTClient.publish(matter, messageJson, 1)
        if args.mode == 'publish':
            print('Revealed matter %s: %sn' % (matter, messageJson))
            loopCount +=1
#lets put the gadget to sleep so it creates disconnect after 60s
print("--- Putting gadget to sleep now, so IoT core keep-alive time expires. ---")
print("--- We'll abruptly disconnect the gadget after 60seconds. ---")

Let’s take a look on the subsequent line which is doing all the work on setting the LWT Topic, JSON payload, and what diploma of QoS we’re using.

myAWSIoTMQTTClient.configureLastWill('/remaining/will/matter', jsonPayload, 0)
  • Topic used is : /remaining/will/matter
  • QoS (Prime quality of Service) is: 0
  • JSON Payload variable includes following payload:
  "state": {
    "reported": {
      "last_will": "certain",
      "trigger_action": "on",
      "client_id": "lwtThing"

The above setup defines the LWT matter along with what matter to submit this message to, which shall be understood and executed by AWS IoT tips as quickly because the gadget disconnects abruptly (The “Last Will” is
printed by the server when its connection to the consumer is unexpectedly misplaced.) An AWS IoT rule will set off the movement on Amazon SNS to ship an e-mail upon its execution. You presumably can study additional on the alternative selections throughout the SDK doc.

We’re setting keep-alive to 30seconds at connection to AWS IoT core so it retains the session alive for the given time. As quickly because the time runs out, the session is expired.

On the expiration of the session, we set the gadget to sleep for 60 seconds, As quickly as 60 seconds finishes we abruptly disconnects the devices which in flip generates Last Will Testament (LWT) set off from AWS IoT Core and message will get printed to all matter subscribers who’re listening to this LWT matter.

Setup Amazon SNS

Let’s setup Amazon SNS and configure it to ship e-mail as its notification, From the Amazon SNS console do the following:

  • Select Issues
    • Select Create matter
      • Select Customary
      • Select Title (i.e. lwtSNSTopic)
      • Select Present establish (i.e. lwtSNSTopic)
      • Select Create matter
    • As quickly as matter is created
      • Select Create subscription
      • Select E-mail from Protocol dropdown
      • For Endpoint give the e-mail cope with you want to use
      • Select Create subscription

It’s best to acquire an e-mail. Please confirm the subscription. When you haven’t confirmed the subscription, you’ll be unable to acquire any emails.

Setup Tips for AWS IoT Core

From the AWS IoT Core console do the following:

  • Select Act
    • Select Tips
    • Select Create
    • Give a establish (i.e. lastWillRule) and description (My first LWT rule)
    • In Rule query assertion enter following:
      • SELECT * FROM '/remaining/will/matter' the place state.reported.last_will="certain" and state.reported.trigger_action = 'on'
    • In Actions half
      • Select Add Movement
      • Select Ship a message to an SNS push notification
      • Select Configure movement
      • In SNS purpose Select the SNS matter you created earlier (i.e. lwtSNSTopic)
      • In Message format, Select JSON
      • Select Create Operate
      • Give it a repute (i.e. lwtRuleRole)
      • Select Add movement

Let’s add one different movement proper right here, we’ll republish the incoming LWT message to a distinct matter to substantiate its incoming.

    • In Actions half
      • Select Add Movement
      • Select Republish a message to an AWS IoT matter
      • Select Configure movement
      • Beneath Topic
        • Select /lwt/executed
        • we’re in a position to depart the Prime quality of Service default
        • For ‘Choose or create a job to grant AWS IoT entry to hold out this movement
          • Select lwtRuleRole
          • Select Change place
        • Select Add movement

This concludes our tips setup half, let’s proceed and setup sending LWT messages and execute our setup.

Sending LWT messages

Sooner than we execute the simulated gadget (using python code) let’s subscribe to the topic throughout the AWS IoT Core console.

Decide 2

Now that we’ve bought each factor in place, let’s execute the IoT Issue (simulated using Python code). You must use the sample execution command which may differ for you as your thingID could possibly be utterly totally different or your certificates path could possibly be in a particular location.

Sample command (alternate xxxx with associated values in your setup):

python -e -r /dwelling/ubuntu/environment/lwt/certs/AmazonRootCA1.pem -c /dwelling/ubuntu/environment/lwt/certs/xxxxxxxxxxxxxxxxxxxxxxxxxxxx-certificate.pem.crt -k /dwelling/ubuntu/environment/lwt/certs/xxxxxxxxxxxxxxxxxxxxxxxxxxxx-private.pem.key -id lwtThing -t /lwt/linked/matter -m publish

What we’re passing as enter parameters to the code is as follows:

  • -e is referring to the tip degree of AWS IoT Core
  • -r is the whole file path the place our Amazon Root CA is positioned
  • -c is the whole file path for our certificates location
  • -k is the whole file path for our personal key
  • -id is the ClientID we’re using to ship to AWS IoT Core (it is advisable match this to what you’ve created the Consider IoT Core as)
  • -t is the topic we’re providing to publish on when it first connects to AWS IoT Core
  • -m is the mode we’ve bought outlined throughout the code and we’ll use publish for this examine. (on the market modes are: publish, subscribe or every)

Let’s take a look on the execution of the command, we should at all times see that LWT is getting configured and what message we printed to AWS IoT Core. Moreover, you will note abrupt disconnect after 60 seconds.

Decide 3

Switching over to the AWS IoT Core console to see incoming messages, subscribe to following issues:

  • Topic used for republishing of the message when the rule is executed (using as debug): /lwt/executed
  • Topic used for when LWT message is printed upon ungraceful disconnect of a consumer: /remaining/will/matter
  • Topic /lwt/linked/matter you’ll be capable to see messages posted by the issue. This occurs when the consumer is linked to AWS IoT Core and sends the message to inform the vendor I’m proper right here and linked.

Decide 4

Beneath matter /remaining/will/matter we’re in a position to see the message executed by AWS IoT Core as quickly because the gadget ungracefully disconnects.

Decide 5

When AWS IoT rule is executed for LWT we’re in a position to see inside matter /lwt/executed payload is printed to this matter too, we configured this matter earlier to repost to when AWS IoT rule is executed upon gadget abrupt disconnection.

Decide 6

Upon worthwhile execution of the AWS IoT rule we moreover triggered Amazon SNS e-mail notification and while you’ve bought configured this appropriately earlier you’ll discover comparable e-mail in your inbox.

Decide 7


On this weblog we checked out how you need to use AWS IoT Core to detect errors and failures of a instrument and abrupt disconnections, and upon abrupt disconnection triggering Amazon SNS e-mail notification to assist employees who can quickly look at and mitigate failure and resolve factors at huge. If the issue closes connection appropriately or in a advisable technique, then AWS IoT Core will disregard the LWT which we set on the time of connection. By using LWT, we’re in a position to implement many error coping with eventualities the place the connection of the consumer drops and the place there’s a dependency of various purchasers relying on this connection chain. As an illustration, when an industrial gateway accountable for gathering sensor data all through the manufacturing facility flooring experiences an abrupt disconnection from AWS IoT Core, you then’ll be capable to monitor these disconnections and take corrective measures to chop again second diploma impression downstream. You presumably can study additional proper right here about MQTT and SNS.

Regarding the author

Syed Rehan is a Sr. Worldwide specialist Choices Architect at Amazon Web Suppliers (AWS) and is based out of London. He’s masking world span of customers and supporting them as lead IoT Reply Architect. Syed has in-depth information of IoT and cloud and works on this place with world prospects ranging from start-up to enterprises to permit them to assemble IoT choices with the AWS eco system.

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