The goal of this project is to show how to add MQTT support to an Azure Sphere project, in this case using the Eclipse Mosquitto MQTT Broker and a PC-based Python application.
| Folder\file | Description |
|---|---|
src\HighLevelApp |
Azure Sphere Sample App source code |
src\HighLevelApp\Certs |
placeholder folder for MQTT certs |
src\PyMqttHost |
Python app that subscribes and publishes messages to a device. |
README.md |
This README file. |
LICENSE.txt |
The license for the project. |
- An Azure Sphere-based device with development features (see Get started with Azure Sphere for more information).
- Setup a development environment for Azure Sphere (see Quickstarts to set up your Azure Sphere device for more information).
- Install Python 3 from Python.org.
- Install the
paho-mqttlibrary usingpip3 install -r requirements.txt.
This sample is made up of two applications, an Azure Sphere MQTT Client application and a Python MQTT host application. The sample uses the public mosquitto.org MQTT broker.
- On startup, the Azure Sphere MQTT-C client connects to the mosquitto.org MQTT broker and subscribes to MQTT messages on topic azuresphere/sample/device. Then every second, the app publishes a message on topic azuresphere/sample/host.
- The Python host application connects to the public mosquitto.org MQTT broker and subscribes to messages on topic azuresphere/sample/host. When a message published by the Azure Sphere mqtt client arrives on the azuresphere/sample/host topic the Python app rotates the message left by one character and publishes the updated message on topic azuresphere/sample/device.
- The Azure Sphere MQTT client subscribed to messages on topic azuresphere/sample/device, it receives the updated message published by the Python app. The Azure Sphere then publishes the updated message back on to topic azuresphere/sample/host.
- And the cycle repeats every one second. From the Azure Sphere debug output window, you can view the echoed message received from the Python app being shifted left one character at a time.
This MQTT sample is going to connect to the mosquitto.org public test MQTT broker. For the Azure Sphere MQTT and Python host MQTT apps to securely connect to the mosquitto.org broker you need to download and copy the mosquitto.org CA certificate and generated client certificates into the Azure Sphere application MQTT-C_Client\src\HighLevelApp\Certs folder.
When you have completed the certificate step you should have three certificate files in the MQTT-C_Client\src\HighLevelApp\Certs folder.
They will be named:
- mosquitto.org.crt
- client.key
- client.crt
For Linux users, you may need to install openssl if it is not installed by default. You can install openssl using your Linux distribution's package manager. For example, on Ubuntu sudo apt-get install openssl.
For Windows users either download openssl from openssl.org, or use WSL (Windows Subsystem for Linux). Depending on the WSL Linux distribution you installed you may need to install openssl. You can install openssl using your Linux distribution's package manager. For example, on Ubuntu sudo apt-get install openssl.
Download the Mosquitto Certificate Authority certificate mosquitto.org.crt (PEM format) and save it in the MQTT-C_Client\src\HighLevelApp\Certs folder.
-
Generate a Certificate Signing Request (CSR) using the openssl utility. Generate a private key:
openssl genrsa -out client.key
-
Generate the CSR:
openssl req -out client.csr -key client.key -new
-
Open the client.csr with your favorite text editor and copy and paste the CSR into the Generate a TLS client certificate form. After you submit the form, the certificate will be generated for you to download. The certificates are valid for 90 days.
-
Save the
client.keyand the downloadedclient.crtinto the MQTT-C_Client\src\HighLevelApp\Certs folder
The project contains a Python application PyMqttHost.py that supports two channels (azuresphere/sample/host and azuresphere/sample/device) one is used by the device to send messages to the host, the other is used by the host to send messages back to the device - feel free to modify the channel names, note that you will need to change the channel names in the HighLevelApp and the Python app.
Start the Python application before running the Azure Sphere application.
The high-level application will connect to the Mosquitto broker and send a message - the host application will receive the message, left shift the message by one character, and return the message to the high-level application. You should see the high-level application output in the Visual Studio/Code debug output window.
The code has been developed to show how to integrate MQTT into an Azure Sphere project - It is not official, maintained, or production-ready code.
This code is not formally maintained, but we will make a best effort to respond to/address any issues you encounter.
If you run into an issue with this code, please open a GitHub issue against this repo.
This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.microsoft.com.
When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repositories using our CLA.
This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.
See LICENSE.txt
- MQTT-C is included via a submodule. The license for MQTT-C can be found here.
- AzureSphereDevX is include via a submodule. The license for AzureSphereDevX can be found here.