Quickstart: Send telemetry from a device to an IoT hub and read it with a back-end application (Node.js)

In this quickstart, you send telemetry from a simulated device application through Azure IoT Hub to a back-end application for processing. IoT Hub is an Azure service that enables you to ingest high volumes of telemetry from your IoT devices into the cloud for storage or processing. This quickstart uses two pre-written Node.js applications: one to send the telemetry and one to read the telemetry from the hub. Before you run these two applications, you create an IoT hub and register a device with the hub.

If you don't have an Azure subscription, create a trial account before you begin.

Prerequisites

  • Node.js 10+.

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

    node --version

  • A sample Node.js project.

  • Port 8883 open in your firewall. The device sample in this quickstart uses MQTT protocol, which communicates over port 8883. This port may be blocked in some corporate and educational network environments. For more information and ways to work around this issue, see Connecting to IoT Hub (MQTT).

You can use the local Azure CLI.

Note

This article uses the newest version of the Azure IoT extension, called azure-iot. The legacy version is called azure-cli-iot-ext. You should only have one version installed at a time. You can use the command az extension list to validate the currently installed extensions.

Use az extension remove --name azure-cli-iot-ext to remove the legacy version of the extension.

Use az extension add --name azure-iot to add the new version of the extension.

To see what extensions are currently installed, use az extension list.

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. On the Azure homepage, select the + Create a resource button.

  3. From the Categories menu, select Internet of Things, and then select IoT Hub.

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

    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.

    Property Value
    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.
    IoT hub name Enter a name for your hub. This name must be globally unique, with a length between 3 and 50 alphanumeric characters. The name can also include the dash ('-') character.
    Region Select the region, closest to you, where you want your hub to be located. Some features, such as IoT Hub device streams, are only available in specific regions. For these limited features, you must select one of the supported regions.
    Tier Select the tier that you want to use for your hub. Tier selection depends on how many features you want and how many messages you send through your solution per day.

    The free tier is intended for testing and evaluation. The free tier allows 500 devices to be connected to the hub and up to 8,000 messages per day. Each Azure subscription can create one IoT hub in the free tier.

    To compare the features available to each tier, select Compare tiers. For more information, see Choose the right IoT Hub tier and size for your solution.
    Daily message limit Select the maximum daily quota of messages for your hub. The available options depend on the tier you select for your hub. To see the available messaging and pricing options, select See all options and select the option that best matches the needs of your hub. For more information, see IoT Hub quotas and throttling.

    Screen capture that shows how to create an IoT hub in the Azure portal.

    Note

    Prices shown are for example purposes only.

  5. Select Next: Networking to continue creating your hub.

  6. On the Networking tab, complete the fields as follows:

    Property Value
    Connectivity configuration Choose the endpoints that devices can use to connect to your IoT hub. Accept the default setting, Public access, for this example. You can change this setting after the IoT hub is created. For more information, see IoT Hub endpoints.
    Minimum TLS Version Select the minimum TLS version supported by your IoT hub. Once the IoT hub is created, this value can't be changed. Accept the default setting, 1.0, for this example.

    Screen capture that shows how to choose the endpoints that can connect to a new IoT hub.

  7. Select Next: Management to continue creating your hub.

  8. On the Management tab, accept the default settings. If desired, you can modify any of the following fields:

    Property Value
    Permission model Part of role-based access control, this property decides how you manage access to your IoT hub. Allow shared access policies or choose only role-based access control. For more information, see Control access to IoT Hub by using Microsoft Entra ID.
    Assign me You might need access to IoT Hub data APIs to manage elements within an instance. If you have access to role assignments, select IoT Hub Data Contributor role to grant yourself full access to the data APIs.

    To assign Azure roles, you must have Microsoft.Authorization/roleAssignments/write permissions, such as User Access Administrator or Owner.
    Device-to-cloud partitions This property relates the device-to-cloud messages to the number of simultaneous readers of the messages. Most IoT hubs need only four partitions.

    Screen capture that shows how to set the role-based access control and scale for a new IoT hub.

  9. Select Next: Add-ons to continue to the next screen.

  10. On the Add-ons tab, accept the default settings. If desired, you can modify any of the following fields:

    Property Value
    Enable Device Update for IoT Hub Turn on Device Update for IoT Hub to enable over-the-air updates for your devices. If you select this option, you're prompted to provide information to provision a Device Update for IoT Hub account and instance. For more information, see What is Device Update for IoT Hub?
    Enable Defender for IoT Turn Defender for IoT on to add an extra layer of protection to IoT and your devices. This option isn't available for hubs in the free tier. For more information, see Security recommendations for IoT Hub in Microsoft Defender for IoT documentation.

    Screen capture that shows how to set the optional add-ons for a new IoT hub.

    Note

    Prices shown are for example purposes only.

  11. Select Next: Tags to continue to the next screen.

    Tags are name/value pairs. You can assign the same tag to multiple resources and resource groups to categorize resources and consolidate billing. In this document, you don't add any tags. For more information, see Use tags to organize your Azure resources and management hierarchy.

    Screen capture that shows how to assign tags for a new IoT hub.

  12. Select Next: Review + create to review your choices.

  13. Select Create to start the deployment of your new hub. Your deployment might progress for a few minutes while the hub is being created. Once the deployment is complete, select Go to resource to open the new hub.

Register a device

A device must be registered with your IoT hub before it can connect. In this quickstart, you use the Azure CLI 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.

    MyNodeDevice: This is the name of the device you're registering. It's recommended to use MyNodeDevice as shown. If you choose a different name for your device, you'll 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 MyNodeDevice

  2. Run the following command to get the device connection string for the device you just registered:

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

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

    Make a note of the device connection string, which looks like:

    HostName={YourIoTHubName}.azure-devices.cn;DeviceId=MyNodeDevice;SharedAccessKey={YourSharedAccessKey}

    You'll use this value later in the quickstart.

  3. You also need the Event Hubs-compatible endpoint, Event Hubs-compatible path, and service primary key from your IoT hub to enable the back-end application to connect to your IoT hub and retrieve the messages. The following commands retrieve these values for your IoT hub:

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

    az iot hub show --query properties.eventHubEndpoints.events.endpoint --name {YourIoTHubName}

az iot hub show --query properties.eventHubEndpoints.events.path --name {YourIoTHubName}

az iot hub policy show --name service --query primaryKey --hub-name {YourIoTHubName}

    Make a note of these three values, which you'll use later in the quickstart.

Send simulated telemetry

The simulated device application connects to a device-specific endpoint on your IoT hub and sends simulated temperature and humidity telemetry.

  1. Open your local terminal window, navigate to the root folder of the sample Node.js project. Then navigate to the iot-hub\Quickstarts\simulated-device folder.

  2. Open the SimulatedDevice.js file in a text editor of your choice.

    Replace the value of the connectionString variable with the device connection string you made a note of earlier. Then save your changes to SimulatedDevice.js.

  3. In the local terminal window, run the following commands to install the required libraries and run the simulated device application:

    npm install
node SimulatedDevice.js

    The following screenshot shows the output as the simulated device application sends telemetry to your IoT hub:

    Run the simulated device

Read the telemetry from your hub

The back-end application connects to the service-side Events endpoint on your IoT Hub. The application receives the device-to-cloud messages sent from your simulated device. An IoT Hub back-end application typically runs in the cloud to receive and process device-to-cloud messages.

  1. Open another local terminal window, navigate to the root folder of the sample Node.js project. Then navigate to the iot-hub\Quickstarts\read-d2c-messages folder.

  2. Open the ReadDeviceToCloudMessages.js file in a text editor of your choice. Update the following variables and save your changes to the file.

    Variable Value
    eventHubsCompatibleEndpoint Replace the value of the variable with the Event Hubs-compatible endpoint you made a note of earlier.
    eventHubsCompatiblePath Replace the value of the variable with the Event Hubs-compatible path you made a note of earlier.
    iotHubSasKey Replace the value of the variable with the service primary key you made a note of earlier.

  3. In the local terminal window, run the following commands to install the required libraries and run the back-end application:

    npm install
node ReadDeviceToCloudMessages.js

    The following screenshot shows the output as the back-end application receives telemetry sent by the simulated device to the hub:

    Run the back-end application

Clean up resources

If you're continuing to the next recommended article, you can keep the resources you already created and reuse them.

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

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 you want to keep, only delete the IoT Hub resource itself instead of deleting the resource group.

To delete a resource group by name:

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

  2. In the Filter for any field textbox, type the name of the resource group containing your IoT hub.

  3. In the result list, select the resource group containing your IoT hub.

  4. In the working pane for the resource group, select Delete resource group from the command bar.

    Screenshot that shows the working pane of a resource group in Azure portal, with the Delete resource group command highlighted in the command bar.

  5. You're asked to confirm the deletion of the resource group. Type the name of your resource group again to confirm, and then select Delete. After a few moments, the resource group and all of its contained resources are deleted.

Next steps

In this quickstart, you set up an IoT hub, registered a device, sent simulated telemetry to the hub using a Node.js application, and read the telemetry from the hub using a simple back-end application.

To learn how to control your simulated device from a back-end application, continue to the next quickstart.

Quickstart: Control a device connected to an IoT hub

  • Last updated on