Quickstart: Communicate to a device application in Node.js via IoT Hub device streams (preview)

Microsoft 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. During public preview, Node.js SDK only supports device streams on the service side. As a result, this quickstart only covers instructions to run the service-side application. You should run an accompanying device-side application from one of the following quickstarts:

The service-side Node.js application in this quickstart has the following functionalities:

  • Creates a device stream to an IoT device.

  • Reads input from command line and sends it to the device application, which will echo it back.

The code will demonstrate the initiation process of a device stream, as well as how to use it to send and receive data.

Use Azure Cloud Shell

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

To launch 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.
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. Launch Cloud Shell.
  2. Select the Copy button on a code block to copy the code.
  3. Paste the code into the Cloud Shell session with Ctrl+Shift+V on Windows and Linux, or Cmd+Shift+V on macOS.
  4. Press 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 only supported for IoT Hubs created in the following regions:

  • Central US

  • Central US EUAP

To run the service-side application in this quickstart you need Node.js v10.x.x or later on your development machine.

You can download Node.js for multiple platforms from Nodejs.org.

You can verify the current version of Node.js on your development machine using the following command:

node --version

Run the following command to add the Microsoft Azure IoT Extension for Azure CLI to your Cloud Shell instance. The IOT Extension adds IoT Hub, IoT Edge, and IoT Device Provisioning Service (DPS) specific commands to Azure CLI.

az extension add --name azure-cli-iot-ext

If you haven't already done so, download the sample Node.js project from https://github.com/Azure-Samples/azure-iot-samples-node/archive/streams-preview.zip and extract the ZIP archive.

Create an IoT hub

If you completed the previous Quickstart: Send telemetry from a device to an IoT hub, you can skip this step.

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

  1. Sign in to the Azure portal.

  2. Select Create a resource, and then select Internet of Things.

  3. In the list at the right, select Iot Hub. The first page for creating an IoT hub opens.

    Creating an IoT hub in the Azure portal

    Fill in the fields:

    a. In the Subscription drop-down list, select the subscription to use for your IoT hub.

    b. For Resource Group, do either of the following:

    • To create a new resource group, select Create new and enter the name you want to use.

    • To use an existing resource group, select Use existing and then, in the drop-down list, select the resource group.

      For more information, see Manage Azure Resource Manager resource groups.

    c. In the Region drop-down list, select 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.

    d. In the IoT Hub Name box, enter the name for your IoT hub. The name must be globally unique. If the name you enter is available, a green check mark appears.

    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.

  4. To continue creating your IoT hub, select Next: Size and scale.

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

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

    • In the Pricing and scale tier drop-down list, 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.

    • For Number of IoT Hub units: This choice depends on non-streaming workload you expect in your hub. You can select 1 for now.

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

  5. To review your choices, select the Review + create tab. The pane that opens is similar to the following:

    Information for creating the new IoT hub

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

Register a device

If you completed the previous Quickstart: Send telemetry from a device to an IoT hub, you can skip this step.

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

  1. Run the following command in Azure Cloud Shell to create the device identity.

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

    MyDevice: This is the name given for the registered device. Use MyDevice as shown. If you choose a different name for your device, you will also need to 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. You also need a service connection string to enable the back-end application to connect to your IoT hub and retrieve the messages. The following command retrieves the service connection string for your IoT hub:

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

    az iot hub show-connection-string --policy-name service --name YourIoTHubName
    

    Make a note of the returned value, which looks like this:

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

Communicate between device and 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 device-side application

As mentioned earlier, IoT Hub Node.js SDK only supports device streams on the service side. For device-side application, use the accompanying device program available in one of these quickstarts:

Ensure the device-side application is running before proceeding to the next step.

Run the service-side application

Assuming the device-side application is running, follow the steps below to run the service-side application in Node.js:

  • Provide your service credentials and device ID as environment variables.

    # In Linux
    export IOTHUB_CONNECTION_STRING="<provide_your_service_connection_string>"
    export STREAMING_TARGET_DEVICE="MyDevice"
    
    # In Windows
    SET IOTHUB_CONNECTION_STRING=<provide_your_service_connection_string>
    SET STREAMING_TARGET_DEVICE=MyDevice
    

    Change MyDevice to the device ID you chose for your device.

  • Navigate to Quickstarts/device-streams-service in your unzipped project folder and run the sample using node.

    cd azure-iot-samples-node-streams-preview/iot-hub/Quickstarts/device-streams-service
    
    # Install the preview service SDK, and other dependencies
    npm install azure-iothub@streams-preview
    npm install
    
    node echo.js
    

At the end of the last step, the service-side program will initiate a stream to your device and once established will send a string buffer to the service over the stream. In this sample, the service-side program simply reads the stdin on the terminal and sends it to the device, which will then echo it back. This demonstrates successful bidirectional communication between the two applications.

Service-side console output

You can then terminate the program by pressing enter again.

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 have set up an IoT hub, registered a device, established a device stream between applications on the device and service side, and used the stream to send data back and forth between the applications.

Use the links below to learn more about device streams: