iot-hub-csharp-csharp-device-management-get-started.md

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Get started with Azure IoT Hub device management (.NET/.NET) | Microsoft Docs	How to use Azure IoT Hub device management to initiate a remote device reboot. You use the Azure IoT device SDK for .NET to implement a simulated device app that includes a direct method and the Azure IoT service SDK for .NET to implement a service app that invokes the direct method.	robinsh	philmea	iot-hub	iot-hub	csharp	conceptual	08/20/2019	robinsh	mqtt, devx-track-csharp

Get started with device management (.NET)

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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 .NET 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 .NET console apps:

• SimulateManagedDevice. This app 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.

• TriggerReboot. This app calls a direct method in the simulated device app, displays the response, and displays the updated reported properties.

Prerequisites

• Visual Studio.

• An active Azure account. If you don't have an account, you can create a free account in just a couple of minutes.

• Make sure that port 8883 is open in your firewall. The device sample in this article 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).

Create an IoT hub

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Register a new device in the IoT hub

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Get the IoT hub connection string

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Trigger a remote reboot on the device using a direct method

In this section, you create a .NET console app, using C#, 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. In Visual Studio, select Create a new project.

2. In Create a new project, find and select the Console App (.NET Framework) project template, and then select Next.

3. In Configure your new project, name the project TriggerReboot, and select .NET Framework version 4.5.1 or later. Select Create.

   

4. In Solution Explorer, right-click the TriggerReboot project, and then select Manage NuGet Packages.

5. Select Browse, then search for and select Microsoft.Azure.Devices. Select Install to install the Microsoft.Azure.Devices package.

   

   This step downloads, installs, and adds a reference to the Azure IoT service SDK NuGet package and its dependencies.

6. Add the following using statements at the top of the Program.cs file:

   using Microsoft.Azure.Devices;
   using Microsoft.Azure.Devices.Shared;

7. Add the following fields to the Program class. Replace the {iot hub connection string} placeholder value with the IoT Hub connection string you copied previously in Get the IoT hub connection string.

   static RegistryManager registryManager;
   static string connString = "{iot hub connection string}";
   static ServiceClient client;
   static string targetDevice = "myDeviceId";

8. Add the following method to the Program class. This code gets the device twin for the rebooting device and outputs the reported properties.

   public static async Task QueryTwinRebootReported()
   {
       Twin twin = await registryManager.GetTwinAsync(targetDevice);
       Console.WriteLine(twin.Properties.Reported.ToJson());
   }

9. Add the following method to the Program class. This code initiates the reboot on the device using a direct method.

   public static async Task StartReboot()
   {
       client = ServiceClient.CreateFromConnectionString(connString);
       CloudToDeviceMethod method = new CloudToDeviceMethod("reboot");
       method.ResponseTimeout = TimeSpan.FromSeconds(30);
   
       CloudToDeviceMethodResult result = await 
         client.InvokeDeviceMethodAsync(targetDevice, method);
   
       Console.WriteLine("Invoked firmware update on device.");
   }

10. Finally, add the following lines to the Main method:

    registryManager = RegistryManager.CreateFromConnectionString(connString);
    StartReboot().Wait();
    QueryTwinRebootReported().Wait();
    Console.WriteLine("Press ENTER to exit.");
    Console.ReadLine();

11. Select Build > Build Solution.

Note

This tutorial performs only a single query for the device's reported properties. In production code, we recommend polling to detect changes in the reported properties.

Create a simulated device app

In this section, you:

• Create a .NET 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 were last rebooted.

To create the simulated device app, follow these steps:

1. In Visual Studio, in the TriggerReboot solution you already created, select File > New > Project. In Create a new project, find and select the Console App (.NET Framework) project template, and then select Next.

2. In Configure your new project, name the project SimulateManagedDevice, and for Solution, select Add to solution. Select Create.

   

3. In Solution Explorer, right-click the new SimulateManagedDevice project, and then select Manage NuGet Packages.

4. Select Browse, then search for and select Microsoft.Azure.Devices.Client. Select Install.

   

   This step downloads, installs, and adds a reference to the Azure IoT device SDK NuGet package and its dependencies.

5. Add the following using statements at the top of the Program.cs file:

   using Microsoft.Azure.Devices.Client;
   using Microsoft.Azure.Devices.Shared;

6. Add the following fields to the Program class. Replace the {device connection string} placeholder value with the device connection string that you noted previously in Register a new device in the IoT hub.

   static string DeviceConnectionString = "{device connection string}";
   static DeviceClient Client = null;

7. Add the following to implement the direct method on the device:

   static Task<MethodResponse> onReboot(MethodRequest methodRequest, object userContext)
   {
       // In a production device, you would trigger a reboot 
       //   scheduled to start after this method returns.
       // For this sample, we simulate the reboot by writing to the console
       //   and updating the reported properties.
       try
       {
           Console.WriteLine("Rebooting!");
   
           // Update device twin with reboot time. 
           TwinCollection reportedProperties, reboot, lastReboot;
           lastReboot = new TwinCollection();
           reboot = new TwinCollection();
           reportedProperties = new TwinCollection();
           lastReboot["lastReboot"] = DateTime.Now;
           reboot["reboot"] = lastReboot;
           reportedProperties["iothubDM"] = reboot;
           Client.UpdateReportedPropertiesAsync(reportedProperties).Wait();
       }
       catch (Exception ex)
       {
           Console.WriteLine();
           Console.WriteLine("Error in sample: {0}", ex.Message);
       }
   
       string result = @"{""result"":""Reboot started.""}";
       return Task.FromResult(new MethodResponse(Encoding.UTF8.GetBytes(result), 200));
   }

8. Finally, add the following code to the Main method to open the connection to your IoT hub and initialize the method listener:

   try
   {
       Console.WriteLine("Connecting to hub");
       Client = DeviceClient.CreateFromConnectionString(DeviceConnectionString, 
         TransportType.Mqtt);
   
       // setup callback for "reboot" method
       Client.SetMethodHandlerAsync("reboot", onReboot, null).Wait();
       Console.WriteLine("Waiting for reboot method\n Press enter to exit.");
       Console.ReadLine();
   
       Console.WriteLine("Exiting...");
   
       // as a good practice, remove the "reboot" handler
       Client.SetMethodHandlerAsync("reboot", null, null).Wait();
       Client.CloseAsync().Wait();
   }
   catch (Exception ex)
   {
       Console.WriteLine();
       Console.WriteLine("Error in sample: {0}", ex.Message);
   }

9. In Solution Explorer, right-click your solution, and then select Set StartUp Projects.

10. For Common Properties > Startup Project, Select Single startup project, and then select the SimulateManagedDevice project. Select OK to save your changes.

11. Select Build > Build Solution.

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 Transient fault handling.

Run the apps

You're now ready to run the apps.

1. To run the .NET device app SimulateManagedDevice, in Solution Explorer, right-click the SimulateManagedDevice project, select Debug, and then select Start new instance. The app should start listening for method calls from your IoT hub.

2. After that the device is connected and waiting for method invocations, right-click the TriggerReboot project, select Debug, and then select Start new instance.

   You should see "Rebooting!" written in the SimulatedManagedDevice console and the reported properties of the device, which include the last reboot time, written in the TriggerReboot console.

   

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