Machine to machine communication with IoT Edge and HiveMQ

Machine to machine communication(M2M) considers two or more machines communicating with each other.
This communication can involve exchanging data, sending commands in order to regulate sensors, raise alarms, start/stop processes, etc., without human interaction.
Some of the protocols that are widely used in M2M communication are MQTT, OPC-UA, CoAP, LWM2M, etc.

Architecture

In scenarios where devices/machines need to exchange data over MQTT broker, Azure IoT Edge can be useful for managing broker and other container deployments(subscribers, data processors, etc) over the cloud. Another role of IoT Edge in these scenarios is to enable a secure connection to the cloud and to send the telemetry to the cloud.
As a broker, HiveMQ broker is used, which is 100% compliant with MQTT standard(including MQTT 5.0), and makes it a perfect option for M2M communication, especially in cases where machines require specific MQTT features.
More about HiveMQ can be found here.
Following example is composed out of the following components:
– Publisher Machine, that sends the telemetry, temperature and humidity
– Subscriber Machine(also can act as a publisher if required), that subscribes to the telemetry topic and reacts on the sensor data from Publisher Machine
– IoT Edge as a module(container) deployment orchestrator and cloud communication gateway
– HiveMQ module(container) as MQTT broker
– Subscriber module, processes telemetry data, before sending to the cloud

 

Architecture of the sample

The architecture of the sample

As a publisher machine, MessageSender was used. This is a UWP application that can send messages to various targets, including the MQTT broker. Any other MQTT client can be used for this purpose.
Subscriber, in this case, is a simple Java application that leverages the HiveMQ library for MQTT brokers.
Following code demonstrates how the topic listener can be implemented with HiveMQ library in Java:

 

The core part of IoT Edge deployment is the manifest file that describes the deployment. HiveMQ can be found on the DockerHub, and the following configuration is an example of how to pull the HiveMQ docker image and start it via IoT Edge deployment.

 

HiveMQ needs to bind 1883 port for MQTT and 8080 for the broker dashboard.
The full code sample with ‘how to run’ instructions can be found on GitHub.
In order to make the sample working, it is required that the publisher and subscriber machines add additional ‘hosts’ configuration:

After running the sample and sending the message from the publisher, the subscriber machine console should show that the message came through the HiveMQ broker deployed on Azure IoT Edge.

Simulation of the Publisher machine

 

The subscriber machine console output after sending the message from the publisher

Finally, the Subscriber Module makes sure that the message ends up on the output, that is passed to the Azure IoT Hub via Routes in Azure IoT Edge Deployment manifest.

 

References:

– HiveMQ documentation: https://www.hivemq.com/docs/4.2/hivemq/introduction.html
– IoT Edge documentation: https://docs.microsoft.com/en-us/azure/iot-edge/

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