IoT Hub
IoT Hub Documentation
Send data to external MQTT brokers
Getting Started Documentation Guides API FAQ

On this page

Send data to external MQTT brokers

This tutorial will show how to send data to external MQTT broker using knob control widget.

Use case

Let’s assume your device is controlling temperature and you would like to use it as an external MQTT broker with the help of IoT Hub.

In this tutorial we will configure IoT Hub Rule Engine to automatically send messages using MQTT protocol. You can use this tutorial as a basis for much more complex tasks.

MQTT Integration allows to convert existing protocols and payload formats to IoT Hub message format and is useful in several deployment scenarios:

  • stream device and/or asset data from external system, IoT platform or connectivity provider back-end.
  • stream device and/or asset data from your custom application running in the cloud.
  • connect the existing device with custom MQTT based protocol to IoT Hub.

Please review the integration diagram to learn more.

image

Prerequisites

We assume you have completed the following guides and reviewed the articles listed below:

Model definition

We will operate with Temperature sensor device that has name “Thermostat-A” and type “thermostat” which will be automatically created in the process of integration work.

image

Getting started

Creating converters

In order for integration to work, downlink and uplink converters should be created.

  • Go to Data Converters -> Add new Data Converter -> Import Converter

image

You can check them like this:

image

Uplink converter should look like this:

image

Downlink converter should look like this:

image

Creating integration

For integration to work a remote server should be used. In this case you can use iot.eclipse.org for your MQTT data. Integration should look like this:

  • Go to Integrations -> Add new Integration

image

  • Fill in the fields with the input data shown in the following table:
FieldInput Data
Name Thermostat MQTT integration
Type MQTT
Debug mode False
Uplink data converter Sensor Uplink Converter
Downlink data converter Sensor Downlink Converter
Host iot.eclipse.org
Port 1883
Connection timeout(sec) 10
Client ID (empty)
Clean session True
Enable SSL False
Credentials Anonymous
Topic filters devices/Thermostat-A/temperature/latest
QOS At most once
Topic filters devices/Thermostat-A/temperature/settings/
QOS At most once
Downlink topic pattern ${topic}
Description (empty)
Metadata (empty)
  • After filling all fields click the ADD button.

image image

Setting up dashboard

Download and import attached json file with a dashboard for this tutorial.

Turning on device emulator

In order for widget to work without a real device, emulator should be turned on.

First, you should check if node, npm and npm module mqtt are installed by using following commands:

1
2
3
4
5
6

#to display node version
node -v
#to display npm version
npm -v
#to display npm mqtt module version
npm list mqtt

If you don’t have npm, you can install it from here, and npm MQTT module with following command:

1

sudo npm install mqtt --save

and node from here.

Download the file and run it with following command to launch device emulator:

1

node mqtt-downlink-virtual-device.js

Note: device emulator should be put in the folder where node-modules is situated.

Work demonstration

image

Using a control widget (in this case, a knob) leads to value change on the dashboard.

Dashboard can be found here and imported like this.

Message Flow

In this section, we explain the purpose of each node in this tutorial.

Modifying rule chain

image

  • Node A: Originator attributes enrichment node

    • Puts client attribute deviceName into metadata

image

  • Node B: Script Transformation Node

    • Puts deviceName from metadata to message parameters

    image

  • Node C: Integration Downlink node

    • Sends message to integration

    image

You can download and import attached json file with a rule chain for this tutorial. It should be marked as root.

Next steps

  • Getting started guides - These guides provide quick overview of main IoT Hub features. Designed to be completed in 15-30 minutes.