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

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. In this quickstart, you send telemetry from a simulated device application, through IoT Hub, to a back-end application for processing.

The 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.

Open Azure Cloud Shell

Azure Cloud Shell is a free, interactive shell that you can use to run the steps in this article. Common Azure tools are preinstalled and configured in Cloud Shell for you to use with your account. Just select the Copy button to copy the code, paste it in Cloud Shell, and then press Enter to run it. There are a few ways to open Cloud Shell:

Select Try It in the upper-right corner of a code block. Cloud Shell in this article
Open Cloud Shell in your browser. https://shell.azure.com/bash
Select the Cloud Shell button on the menu in the upper-right corner of the Azure portal. Cloud Shell in the portal

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

Prerequisites

The two sample applications you run in this quickstart are written using Node.js. You need Node.js v4.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

Download the sample Node.js project from https://github.com/Azure-Samples/azure-iot-samples-node/archive/master.zip and extract the ZIP archive.

Create an IoT hub

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

  1. Log in to the Azure portal.

  2. Choose +Create a resource, then choose Internet of Things.

  3. Click Iot Hub from the list on the right. You see the first screen for creating an IoT hub.

    Screenshot showing creating a hub in the Azure portal

    Fill in the fields.

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

    Resource Group: You can create a new resource group or use an existing one. To create a new one, click Create new and fill in the name you want to use. To use an existing resource group, click Use existing and select the resource group from the dropdown list. For more information, see Use resource groups to manage your Azure resources.

    Region: This is the region in which you want your hub to be located. Select the location closest to you from the dropdown list.

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

    Important

    The IoT hub will be publicly discoverable as a DNS endpoint, so make sure to avoid any sensitive information while naming it.

  4. Click Next: Size and scale to continue creating your IoT hub.

    Screenshot showing setting size and scale for a new IoT hub using the Azure portal

    On this screen, you can take the defaults and just click Review + create at the bottom.

    Pricing and scale tier: You can choose from several tiers depending 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. 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.

    IoT Hub units: The number of messages allowed per unit per day depends on your hub's pricing tier. For example, if you want the IoT hub to support ingress of 700,000 messages, you choose two S1 tier units.

    For details about the other tier options, see Choosing the right IoT Hub tier.

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

  5. Click Review + create to review your choices. You see something similar to this screen.

    Screenshot reviewing information for creating the new IoT hub

  6. Click Create to create your new IoT hub. Creating the hub takes a few minutes.

Register a device

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 commands in Azure Cloud Shell to add the IoT Hub CLI extension and to create the device identity.

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

    MyNodeDevice : This is the name given for the registered device. Use MyNodeDevice 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 extension add --name azure-cli-iot-ext
    az iot hub device-identity create --hub-name YourIoTHubName --device-id MyNodeDevice
    
  2. Run the following commands in Azure Cloud Shell to get the device connection string for the device you just registered:

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

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

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

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

    You use this value later in the quickstart.

  3. You also need a service connection string to enable the back-end application to connect to your IoT hub in order to retrieve the messages. The following command retrieves the service connection string for your IoT hub:

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

    az iot hub show-connection-string --hub-name YourIoTHubName --output table
    

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

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

    You use this value later in the quickstart. The service connection string is different from the device connection string.

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 previously. Then save your changes to SimulatedDevice.js file.

  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.

    Replace the value of the connectionString variable with the service connection string you made a note of previously. Then save your changes to the ReadDeviceToCloudMessages.js file.

  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 will be continuing to the next recommended article, you can keep the resources you've 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 do not 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 click Resource groups.

  2. In the Filter by name... textbox, type the name of the resource group containing your IoT Hub.

  3. To the right of your resource group in the result list, click ... then Delete resource group.

    Delete

  4. You will be asked to confirm the deletion of the resource group. Type the name of your resource group again to confirm, and then click Delete. After a few moments, the resource group and all of its contained resources are deleted.

Next steps

In this quickstart, you've setup 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.