Quickstart: Communicate to a device application in C# via IoT Hub device streams (preview)

Azure IoT Hub currently supports device streams as a preview feature.

IoT Hub device streams allow service and device applications to communicate in a secure and firewall-friendly manner. This quickstart involves two C# applications that take advantage of device streams to send data back and forth (echo).

Use Azure Cloud Shell

Azure hosts Azure Cloud Shell, an interactive shell environment that you can use through your browser. You can use either Bash or PowerShell with Cloud Shell to work with Azure services. You can use the Cloud Shell preinstalled commands to run the code in this article without having to install anything on your local environment.

To start Azure Cloud Shell:

Option Example/Link
Select Try It in the upper-right corner of a code block. Selecting Try It doesn't automatically copy the code to Cloud Shell. Example of Try It for Azure Cloud Shell
Go to https://shell.azure.com, or select the Launch Cloud Shell button to open Cloud Shell in your browser. Launch Cloud Shell in a new window
Select the Cloud Shell button on the top-right menu bar in the Azure portal. Cloud Shell button in the Azure portal

To run the code in this article in Azure Cloud Shell:

  1. Start Cloud Shell.

  2. Select the Copy button on a code block to copy the code.

  3. Paste the code into the Cloud Shell session by selecting Ctrl+Shift+V on Windows and Linux or by selecting Cmd+Shift+V on macOS.

  4. Select Enter to run the code.

If you don’t have an Azure subscription, create a free account before you begin.

Prerequisites

  • The preview of device streams is currently supported only for IoT hubs that are created in the following regions:

    • Central US
    • Central US EUAP
    • North Europe
    • Southeast Asia
  • The two sample applications that you run in this quickstart are written in C#. You need the .NET Core SDK 2.1.0 or later on your development machine.

    dotnet --version
    
  • Add the Azure IoT Extension for Azure CLI to your Cloud Shell instance by running the following command. The IOT Extension adds IoT Hub, IoT Edge, and IoT Device Provisioning Service (DPS)-specific commands to the Azure CLI.

    az extension add --name azure-cli-iot-ext
    
  • Download the sample C# project and extract the ZIP archive. You need it on both the device side and the service side.

Create an IoT hub

This section describes how to create an IoT hub using the Azure portal.

  1. Sign in to the Azure portal.

  2. Choose Create a resource, and then enter IoT Hub in the Search the Marketplace field.

  3. Select IoT Hub from the search results, and then select Create.

  4. On the Basics tab, complete the fields as follows:

    • Subscription: Select the subscription to use for your hub.

    • Resource Group: Select a resource group or create a new one. To create a new one, select Create new and fill in the name you want to use. To use an existing resource group, select that resource group. For more information, see Manage Azure Resource Manager resource groups.

    • Region: Choose the region in which you want your hub to be located. Select a region that supports the IoT Hub device streams preview, either Central US or Central US EUAP.

    • IoT Hub Name: Enter a name for your hub. This name must be globally unique. If the name you enter is available, a green check mark appears.

    Creating an IoT hub in the Azure portal

    Important

    Because the IoT hub will be publicly discoverable as a DNS endpoint, be sure to avoid entering any sensitive or personally identifiable information when you name it.

  5. Select Next: Size and scale to continue creating your hub.

    Setting size and scale for a new IoT hub using the Azure portal

    In Size and scale, you can accept the default settings and select Review + create at the bottom. Consider the following options:

    • Pricing and scale tier: Your selected tier. Select one of the standard tiers (S1, S2, or S3) or F1: Free tier. This choice can also be guided by the size of your fleet and the non-streaming workloads that you expect in your hub, for example, telemetry messages. For example, the free tier is intended for testing and evaluation. It allows 500 devices to be connected to the IoT hub and up to 8,000 messages per day. Each Azure subscription can create one IoT hub in the free tier.

    • Number of IoT Hub units: The number of messages allowed per unit per day depends on your hub's pricing tier. This choice depends on non-streaming workload you expect in your hub. You can select 1 for now.

    • Advanced Settings > Device-to-cloud partitions: This property relates the device-to-cloud messages to the number of simultaneous readers of the messages. Most hubs only need four partitions.

    For more information about tier options, see Choose the right IoT hub tier.

  6. To review your choices, choose Review + create. Your results will be similar to the following:

    Information for creating the new IoT hub

  7. To create your new IoT hub, select Create. The process takes a few minutes.

Register a device

A device must be registered with your IoT hub before it can connect. In this section, you use Azure Cloud Shell to register a simulated device.

  1. To create the device identity, run the following command in Cloud Shell:

    Note

    • Replace the YourIoTHubName placeholder with the name you chose for your IoT hub.
    • For the name of the device you're registering, it's recommended to use MyDevice as shown. If you choose a different name for your device, use that name throughout this article, and update the device name in the sample applications before you run them.
    az iot hub device-identity create --hub-name {YourIoTHubName} --device-id MyDevice
    
  2. To get the device connection string for the device that you just registered, run the following command in Cloud Shell:

    Note

    Replace the YourIoTHubName placeholder with the name you chose for your IoT hub.

    az iot hub device-identity show-connection-string --hub-name {YourIoTHubName} --device-id MyDevice --output table
    

    Note the returned device connection string for later use in this quickstart. It looks like the following example:

    HostName={YourIoTHubName}.azure-devices.net;DeviceId=MyDevice;SharedAccessKey={YourSharedAccessKey}

  3. You also need the service connection string from your IoT hub to enable the service-side application to connect to your IoT hub and establish a device stream. The following command retrieves this value for your IoT hub:

    Note

    Replace the YourIoTHubName placeholder with the name you chose for your IoT hub.

    az iot hub show-connection-string --policy-name service --name {YourIoTHubName} --output table
    

    Note the returned service connection string for later use in this quickstart. It looks like the following example:

    "HostName={YourIoTHubName}.azure-devices.net;SharedAccessKeyName=service;SharedAccessKey={YourSharedAccessKey}"

Communicate between the device and the service via device streams

In this section, you run both the device-side application and the service-side application and communicate between the two.

Run the service-side application

In a local terminal window, navigate to the iot-hub/Quickstarts/device-streams-echo/service directory in your unzipped project folder. Keep the following information handy:

Parameter name Parameter value
ServiceConnectionString The service connection string of your IoT hub.
MyDevice The identifier of the device you created earlier.

Compile and run the code with the following commands:

cd ./iot-hub/Quickstarts/device-streams-echo/service/

# Build the application
dotnet build

# Run the application
# In Linux or macOS
dotnet run "{ServiceConnectionString}" "MyDevice"

# In Windows
dotnet run {ServiceConnectionString} MyDevice

The application will wait for the device application to become available.

Note

A timeout occurs if the device-side application doesn't respond in time.

Run the device-side application

In another local terminal window, navigate to the iot-hub/Quickstarts/device-streams-echo/device directory in your unzipped project folder. Keep the following information handy:

Parameter name Parameter value
DeviceConnectionString The device connection string of your IoT Hub.

Compile and run the code with the following commands:

cd ./iot-hub/Quickstarts/device-streams-echo/device/

# Build the application
dotnet build

# Run the application
# In Linux or macOS
dotnet run "{DeviceConnectionString}"

# In Windows
dotnet run {DeviceConnectionString}

At the end of the last step, the service-side application initiates a stream to your device. After the stream is established, the application sends a string buffer to the service over the stream. In this sample, the service-side application simply echoes back the same data to the device, which demonstrates a successful bidirectional communication between the two applications.

Console output on the device side:

Console output on the device side

Console output on the service side:

Console output on the service side

The traffic being sent over the stream is tunneled through the IoT hub rather than sent directly. The benefits provided are detailed in Device streams benefits.

Clean up resources

If you plan to continue to the next recommended article, you can keep and reuse the resources you've already created.

Otherwise, to avoid charges, you can delete the Azure resources that you created in this article.

Important

Deleting a resource group is irreversible. The resource group and all the resources contained in it are permanently deleted. Make sure that you don't accidentally delete the wrong resource group or resources. If you created the IoT hub inside an existing resource group that contains resources that you want to keep, delete only the IoT hub resource itself, not the resource group.

To delete a resource group by name:

  1. Sign in to the Azure portal, and then select Resource groups.

  2. In the Filter by name box, enter the name of the resource group that contains your IoT hub.

  3. In the result list, to the right of your resource group, select the ellipsis (...), and then select Delete resource group.

    The "Delete resource group" button

  4. To confirm the deletion of the resource group, reenter the resource group name, and then select Delete. After a few moments, the resource group and all its contained resources are deleted.

Next steps

In this quickstart, you set up an IoT hub, registered a device, established a device stream between C# applications on the device and service sides, and used the stream to send data back and forth between the applications.

To learn more about device streams, see: