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Get started with Azure IoT Hub device management (Node) | Microsoft Docs
How to use IoT Hub device management to initiate a remote device reboot. You use the Azure IoT SDK for Node.js to implement a simulated device app that includes a direct method and a service app that invokes the direct method.
juanjperez
cberlin
iot-hub
iot-hub
conceptual
08/25/2017
juanpere

Get started with device management (Node)

[!INCLUDE iot-hub-selector-dm-getstarted]

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

[!INCLUDE iot-hub-include-create-hub]

Retrieve connection string for IoT hub

[!INCLUDE iot-hub-include-find-connection-string]

[!INCLUDE iot-hub-get-started-create-device-identity]

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.

[!INCLUDE iot-hub-dm-followup]