Quickstart: Send telemetry from a device to an IoT hub (iOS)

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 article, you send telemetry from a simulated device application to IoT Hub. Then you can view the data from a back-end application.

This article uses a pre-written Swift application to send the telemetry and a CLI utility to read the telemetry from IoT Hub.

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

  • Download the code sample from Azure samples

  • The latest version of XCode, running the latest version of the iOS SDK. This quickstart was tested with XCode 10.2 and iOS 12.2.

  • The latest version of CocoaPods.

  • 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
    

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. From the Azure homepage, select the + Create a resource button, 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: Select the region in which you want your hub to be located. Select the location closest to you.

    • 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.

    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.

    Create a hub in the Azure portal

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

    Set the size and scale for a new hub using the Azure portal

    This screen allows you to set the following values:

    • Pricing and scale tier: Your selected 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 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 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 Settings > Device-to-cloud partitions: This property relates the device-to-cloud messages to the number of simultaneous readers of the messages. Most hubs need only four partitions.

  6. For this article, accept the default choices, and then select Review + create to review your choices. You see something similar to this screen.

    Review information for creating the new hub

  7. Select Create to create your new 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 command in Azure Cloud Shell to create the device identity.

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

    myiOSdevice: This is the name of the device you're registering. It's recommended to use myiOSdevice 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 myiOSdevice
    
  2. Run the following command 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 chose for your IoT hub.

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

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

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

    You'll use this value later in the quickstart.

Send simulated telemetry

The sample application runs on an iOS device, which connects to a device-specific endpoint on your IoT hub and sends simulated temperature and humidity telemetry.

Install CocoaPods

CocoaPods manage dependencies for iOS projects that use third-party libraries.

In a local terminal window, navigate to the Azure-IoT-Samples-iOS folder that you downloaded in the prerequisites. Then, navigate to the sample project:

cd quickstart/sample-device

Make sure that XCode is closed, then run the following command to install the CocoaPods that are declared in the podfile file:

pod install

Along with installing the pods required for your project, the installation command also created an XCode workspace file that is already configured to use the pods for dependencies.

Run the sample application

  1. Open the sample workspace in XCode.

    open "MQTT Client Sample.xcworkspace"
    
  2. Expand the MQTT Client Sample project and then expand the folder of the same name.

  3. Open ViewController.swift for editing in XCode.

  4. Search for the connectionString variable and update the value with the device connection string that you made a note of earlier.

  5. Save your changes.

  6. Run the project in the device emulator with the Build and run button or the key combo command + r.

    Run the project

  7. When the emulator opens, select Start in the sample app.

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

Run the simulated device

Read the telemetry from your hub

The sample app that you ran on the XCode emulator shows data about messages sent from the device. You can also view the data through your IoT hub as it is received. The IoT Hub CLI extension can connect to the service-side Events endpoint on your IoT Hub. The extension 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.

Run the following commands in Azure Cloud Shell, replacing YourIoTHubName with the name of your IoT hub:

az iot hub monitor-events --device-id myiOSdevice --hub-name {YourIoTHubName}

The following screenshot shows the output as the extension receives telemetry sent by the simulated device to the hub:

The following screenshot shows the type of telemetry that you see in your local terminal window:

View telemetry

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 select 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, select ... 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 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 from an iOS device, and read the telemetry from the hub.

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