Example: Using the Azure IoT Hub Client SL Library

Set up the "Azure IoT Hub" and create devices in the "Azure IoT Hub".

Generate "Shared Access Signatures" (SaS tokens).

A device is authenticated via "Shared Access Signatures" (SaS tokens).

For access via MQTT, an SaS token based on the "device" policy is required.

Access via HTTPS requires an SaS token based on the "device" policy and an SaS token based on the "iothubowner" policy.

The SaS token can be generated via the Azure Cloud Shell (Azure Portal), via the "Azure IoT Explorer" tool, or directly via the GenerateSasToken library function.

The GenerateSasToken function takes 4 input parameters (URL address, Primary Key, Policy Name, Expiry) and returns an SaS token as WSTRING(255).

1. Start the Cloud Shell from the Azure Portal.

   

2. Generate a device SaS token:

   az iot hub generate-sas-token -d YOUR_DEVICE_ID -n YOUR_IOT_HUB --du DURATION_IN_SECONDS --policy device

3. Generate the iothubowner SaS token:

   az iot hub generate-sas-token -n YOUR_IOT_HUB --du DURATION_IN_SECONDS

   Figure 10. Generated SaS tokens

   
   
   

In the sample project, set the names of the IoT Hub, DeviceId, and SaS tokens:

sSubDomainName: Name of the "Azure IoT Hub" without "azure-devices.net" (see Step 1)

sDeviceId: ID of the device

wsDeviceSaS: SaS token of the device (MQTT, HTTP) (see Step 2)

wsIoTHubOwnerSaS: SaS token of the IoT Hub Owner (HTTP) (see Step 2)

Download the project to the controller and start the applications.

1. Start the AzureHTTPDemo application.

   You can execute the following functions via the visualization:

   Send D2C Message

   Get C2D Message

   Get Device Twin

   Update Device Twin

2. Start the AzureMQTTDemo application.

   You can execute the following functions via the visualization:

   • Establishing an MQTT connection

   • Send D2C Message

   • Get C2D Message

   • Get Device Twin

   • Update Device Twin

   • Method call: Direct method call

   • Subscribe Device Twin (desired)

You send and receive messages using the Azure IoT Explorer tool.

The Azure IoT Explorer tool can be used to view and send messages. You can find the download link for it below.

Figure 11. Azure IoT Explorer: Monitoring of D2C messages

Figure 12. Azure IoT Explorer: Sending of D2C messages

Figure 13. Azure IoT Explorer: Remote method call