Get started with device management (Node)

Back-end apps can use Azure IoT Hub primitives, such as device twin and direct methods, to remotely start and monitor device management actions on devices. This tutorial shows you how a back-end app and a device app can work together to initiate and monitor a remote device reboot using IoT Hub.

Note

The features described in this article are only available in the standard tier of IoT hub. For more information about the basic and standard IoT Hub tiers, see How to choose the right IoT Hub tier.

Use a direct method to initiate device management actions (such as reboot, factory reset, and firmware update) from a back-end app in the cloud. The device is responsible for:

  • Handling the method request sent from IoT Hub.
  • Initiating the corresponding device-specific action on the device.
  • Providing status updates through reported properties to IoT Hub.

You can use a back-end app in the cloud to run device twin queries to report on the progress of your device management actions.

This tutorial shows you how to:

  • Use the Azure portal to create an IoT Hub and create a device identity in your IoT hub.
  • Create a simulated device app that contains a direct method that reboots that device. Direct methods are invoked from the cloud.
  • Create a Node.js console app that calls the reboot direct method in the simulated device app through your IoT hub.

At the end of this tutorial, you have two Node.js console apps:

dmpatterns_getstarted_device.js, which connects to your IoT hub with the device identity created earlier, receives a reboot direct method, simulates a physical reboot, and reports the time for the last reboot.

dmpatterns_getstarted_service.js, which calls a direct method in the simulated device app, displays the response, and displays the updated reported properties.

To complete this tutorial, you need the following:

  • Node.js version 4.0.x or later,
    Prepare your development environment describes how to install Node.js for this tutorial on either Windows or Linux.
  • An active Azure account. (If you don't have an account, you can create a free account in just a couple of minutes.)

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.

Retrieve connection string for IoT hub

After your hub has been created, retrieve the connection string for the hub. This is used to connect devices and applications to your hub.

  1. Click on your hub to see the IoT Hub pane with Settings, and so on. Click Shared access policies.

  2. In Shared access policies, select the iothubowner policy.

  3. Under Shared access keys, copy the Connection string -- primary key to be used later.

    Show how to retrieve the connection string

    For more information, see Access control in the "IoT Hub developer guide."

Create a device identity

In this section, you use the Azure CLI to create a device identity for this tutorial. The Azure CLI is preinstalled in the Azure Cloud Shell, or you can install it locally. Device IDs are case sensitive.

  1. Run the following command in the command-line environment where you are using the Azure CLI to install the IoT extension:

    az extension add --name azure-cli-iot-ext
    
  2. If you are running the Azure CLI locally, use the following command to sign in to your Azure account (if you are using the Cloud Shell, you are signed in automatically and you don't need to run this command):

    az login
    
  3. Finally, create a new device identity called myDeviceId and retrieve the device connection string with these commands:

    az iot hub device-identity create --device-id myDeviceId --hub-name {Your IoT Hub name}
    az iot hub device-identity show-connection-string --device-id myDeviceId --hub-name {Your IoT Hub name} -o table
    

    Important

    The device ID may be visible in the logs collected for customer support and troubleshooting, so make sure to avoid any sensitive information while naming it.

Make a note of the device connection string from the result. This device connection string is used by the device app to connect to your IoT Hub as a device.

Create a simulated device app

In this section, you will

  • Create a Node.js console app that responds to a direct method called by the cloud
  • Trigger a simulated device reboot
  • Use the reported properties to enable device twin queries to identify devices and when they last rebooted
  1. Create an empty folder called manageddevice. In the manageddevice folder, create a package.json file using the following command at your command prompt. Accept all the defaults:

    npm init
    
  2. At your command prompt in the manageddevice folder, run the following command to install the azure-iot-device Device SDK package and azure-iot-device-mqtt package:

    npm install azure-iot-device azure-iot-device-mqtt --save
    
  3. Using a text editor, create a dmpatterns_getstarted_device.js file in the manageddevice folder.
  4. Add the following 'require' statements at the start of the dmpatterns_getstarted_device.js file:

    'use strict';
    
    var Client = require('azure-iot-device').Client;
    var Protocol = require('azure-iot-device-mqtt').Mqtt;
    
  5. Add a connectionString variable and use it to create a Client instance. Replace the connection string with your device connection string.

    var connectionString = 'HostName={youriothostname};DeviceId=myDeviceId;SharedAccessKey={yourdevicekey}';
    var client = Client.fromConnectionString(connectionString, Protocol);
    
  6. Add the following function to implement the direct method on the device

    var onReboot = function(request, response) {
    
        // Respond the cloud app for the direct method
        response.send(200, 'Reboot started', function(err) {
            if (err) {
                console.error('An error occured when sending a method response:\n' + err.toString());
            } else {
                console.log('Response to method \'' + request.methodName + '\' sent successfully.');
            }
        });
    
        // Report the reboot before the physical restart
        var date = new Date();
        var patch = {
            iothubDM : {
                reboot : {
                    lastReboot : date.toISOString(),
                }
            }
        };
    
        // Get device Twin
        client.getTwin(function(err, twin) {
            if (err) {
                console.error('could not get twin');
            } else {
                console.log('twin acquired');
                twin.properties.reported.update(patch, function(err) {
                    if (err) throw err;
                    console.log('Device reboot twin state reported')
                });  
            }
        });
    
        // Add your device's reboot API for physical restart.
        console.log('Rebooting!');
    };
    
  7. Open the connection to your IoT hub and start the direct method listener:

    client.open(function(err) {
        if (err) {
            console.error('Could not open IotHub client');
        }  else {
            console.log('Client opened.  Waiting for reboot method.');
            client.onDeviceMethod('reboot', onReboot);
        }
    });
    
  8. Save and close the dmpatterns_getstarted_device.js file.

Note

To keep things simple, this tutorial does not implement any retry policy. In production code, you should implement retry policies (such as an exponential backoff), as suggested in the article, Transient Fault Handling.

Trigger a remote reboot on the device using a direct method

In this section, you create a Node.js console app that initiates a remote reboot on a device using a direct method. The app uses device twin queries to discover the last reboot time for that device.

  1. Create an empty folder called triggerrebootondevice. In the triggerrebootondevice folder, create a package.json file using the following command at your command prompt. Accept all the defaults:

    npm init
    
  2. At your command prompt in the triggerrebootondevice folder, run the following command to install the azure-iothub Device SDK package and azure-iot-device-mqtt package:

    npm install azure-iothub --save
    
  3. Using a text editor, create a dmpatterns_getstarted_service.js file in the triggerrebootondevice folder.
  4. Add the following 'require' statements at the start of the dmpatterns_getstarted_service.js file:

    'use strict';
    
    var Registry = require('azure-iothub').Registry;
    var Client = require('azure-iothub').Client;
    
  5. Add the following variable declarations and replace the placeholder values:

    var connectionString = '{iothubconnectionstring}';
    var registry = Registry.fromConnectionString(connectionString);
    var client = Client.fromConnectionString(connectionString);
    var deviceToReboot = 'myDeviceId';
    
  6. Add the following function to invoke the device method to reboot the target device:

    var startRebootDevice = function(twin) {
    
        var methodName = "reboot";
    
        var methodParams = {
            methodName: methodName,
            payload: null,
            timeoutInSeconds: 30
        };
    
        client.invokeDeviceMethod(deviceToReboot, methodParams, function(err, result) {
            if (err) { 
                console.error("Direct method error: "+err.message);
            } else {
                console.log("Successfully invoked the device to reboot.");  
            }
        });
    };
    
  7. Add the following function to query for the device and get the last reboot time:

    var queryTwinLastReboot = function() {
    
        registry.getTwin(deviceToReboot, function(err, twin){
    
            if (twin.properties.reported.iothubDM != null)
            {
                if (err) {
                    console.error('Could not query twins: ' + err.constructor.name + ': ' + err.message);
                } else {
                    var lastRebootTime = twin.properties.reported.iothubDM.reboot.lastReboot;
                    console.log('Last reboot time: ' + JSON.stringify(lastRebootTime, null, 2));
                }
            } else 
                console.log('Waiting for device to report last reboot time.');
        });
    };
    
  8. Add the following code to call the functions that trigger the reboot direct method and query for the last reboot time:

    startRebootDevice();
    setInterval(queryTwinLastReboot, 2000);
    
  9. Save and close the dmpatterns_getstarted_service.js file.

Run the apps

You are now ready to run the apps.

  1. At the command prompt in the manageddevice folder, run the following command to begin listening for the reboot direct method.

    node dmpatterns_getstarted_device.js
    
  2. At the command prompt in the triggerrebootondevice folder, run the following command to trigger the remote reboot and query for the device twin to find the last reboot time.

    node dmpatterns_getstarted_service.js
    
  3. You see the device response to the direct method in the console.

Customize and extend the device management actions

Your IoT solutions can expand the defined set of device management patterns or enable custom patterns by using the device twin and cloud-to-device method primitives. Other examples of device management actions include factory reset, firmware update, software update, power management, network and connectivity management, and data encryption.

Device maintenance windows

Typically, you configure devices to perform actions at a time that minimizes interruptions and downtime. Device maintenance windows are a commonly used pattern to define the time when a device should update its configuration. Your back-end solutions can use the desired properties of the device twin to define and activate a policy on your device that enables a maintenance window. When a device receives the maintenance window policy, it can use the reported property of the device twin to report the status of the policy. The back-end app can then use device twin queries to attest to compliance of devices and each policy.

Next steps

In this tutorial, you used a direct method to trigger a remote reboot on a device. You used the reported properties to report the last reboot time from the device, and queried the device twin to discover the last reboot time of the device from the cloud.

To continue getting started with IoT Hub and device management patterns such as remote over the air firmware update, see:

Tutorial: How to do a firmware update

To learn how to extend your IoT solution and schedule method calls on multiple devices, see the Schedule and broadcast jobs tutorial.

To continue getting started with IoT Hub, see Getting started with IoT Edge.