Handling Appservice connections in a multiple instance of fulltrust process

Question

Hello UWP experts,

Please look at the below thread . This question is related to the thread.

https://learn.microsoft.com/en-us/answers/questions/2087088/uwp-app-communication-with-another-process-(*-exe)?comment=question#newest-question-comment

UWP app will start multiple instances of fulltrust process each will start the Appservice server. How to differentiate Appservice service for Appservice connections started from UWP?

Thanks

Answer 1

Hello @DotNET Fan ,

This is my test code for your reference. I use WPF project as fulltrust process. Appservice can be used normally.

In WPF(.net 7.0),

 private AppServiceConnection connection = null;
 public MainWindow()
 {
     InitializeComponent();
     InitializeAppServiceConnection();
 }
 private async void InitializeAppServiceConnection()
 {
     connection = new AppServiceConnection();
     connection.AppServiceName = "SampleInteropService";
     connection.PackageFamilyName = Package.Current.Id.FamilyName;
     connection.RequestReceived += Connection_RequestReceived;
     connection.ServiceClosed += Connection_ServiceClosed;
     AppServiceConnectionStatus status = await connection.OpenAsync();
     if (status != AppServiceConnectionStatus.Success)
     {
         // something went wrong ...
         MessageBox.Show(status.ToString());
         this.IsEnabled = false;
     }
 }

Add Extensions in WAPP Package.appxmanifest.

   <Extensions>
     <desktop:Extension Category="windows.fullTrustProcess" 
                           Executable="WPFfulltrust\WPFfulltrust.exe"/>
     <uap:Extension Category="windows.appService">
        <uap:AppService Name="SampleInteropService" />
     </uap:Extension>
   </Extensions>  

In UWP App.xaml.cs, activate the UWP in the background and establish the AppServiceConnection.

 public static BackgroundTaskDeferral AppServiceDeferral = null;
 public static AppServiceConnection Connection = null;
 public static event EventHandler AppServiceDisconnected;
 public static event EventHandler<AppServiceTriggerDetails> AppServiceConnected;
 public static bool IsForeground = false;
 /// <summary>
 /// Initializes the singleton application object.  This is the first line of authored code
 /// executed, and as such is the logical equivalent of main() or WinMain().
 /// </summary>
 public App()
 {
     this.InitializeComponent();
     this.Suspending += OnSuspending;
     this.EnteredBackground += App_EnteredBackground;
     this.LeavingBackground += App_LeavingBackground;
 }
 private void App_LeavingBackground(object sender, LeavingBackgroundEventArgs e)
 {
     IsForeground = true;
 }
 private void App_EnteredBackground(object sender, EnteredBackgroundEventArgs e)
 {
     IsForeground = false;
 }
 protected override void OnBackgroundActivated(BackgroundActivatedEventArgs args)
 {
     base.OnBackgroundActivated(args);
     if (args.TaskInstance.TriggerDetails is AppServiceTriggerDetails details)
     {
         // only accept connections from callers in the same package
         if (details.CallerPackageFamilyName == Package.Current.Id.FamilyName)
         {
             // connection established from the fulltrust process
             AppServiceDeferral = args.TaskInstance.GetDeferral();
             args.TaskInstance.Canceled += OnTaskCanceled;
             Connection = details.AppServiceConnection;
             AppServiceConnected?.Invoke(this, args.TaskInstance.TriggerDetails as AppServiceTriggerDetails);
         }
     }
 }
 private void OnTaskCanceled(IBackgroundTaskInstance sender, BackgroundTaskCancellationReason reason)
 {
     AppServiceDeferral?.Complete();
     AppServiceDeferral = null;
     Connection = null;
     AppServiceDisconnected?.Invoke(this, null);
 }

In UWP MainPage, send message.

protected async override void OnNavigatedTo(NavigationEventArgs e)
{
    base.OnNavigatedTo(e);
    if (ApiInformation.IsApiContractPresent("Windows.ApplicationModel.FullTrustAppContract", 1, 0))
    {
        App.AppServiceConnected += MainPage_AppServiceConnected;
        App.AppServiceDisconnected += MainPage_AppServiceDisconnected;
        await FullTrustProcessLauncher.LaunchFullTrustProcessForCurrentAppAsync();
    }
}
/// <summary>
/// When the desktop process is connected, get ready to send/receive requests
/// </summary>
private async void MainPage_AppServiceConnected(object sender, AppServiceTriggerDetails e)
{
    App.Connection.RequestReceived += AppServiceConnection_RequestReceived;
    await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
    {
        // enable UI to access  the connection
        btnRegKey.IsEnabled = true;
    });
}

 private async void btnClick_ReadKey(object sender, RoutedEventArgs e)
 {
     ValueSet request = new ValueSet();
     request.Add("KEY", tbKey.Text);
     AppServiceResponse response = await App.Connection.SendMessageAsync(request);
     // display the response key/value pairs
     tbResult.Text = "";
     foreach (string key in response.Message.Keys)
     {
         tbResult.Text += key + " = " + response.Message[key] + "\r\n";
     }
 }

This code refers to StefanWick's blog and code.

Feel free to comment on how there are other questions.

Thank you.

---

If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

Hello @DotNET Fan ,

Welcome to Microsoft Q&A!

You can use AppServiceConnection.SendMessageAsync to send a special ID, such as file name + time.

var message = new ValueSet(); 
message.Add("Fileinfo", "Name+Time"); 
AppServiceResponse response = await this.inventoryService.SendMessageAsync(message);

Then read the passed parameters from args in OnRequestReceived.

var messageDeferral = args.GetDeferral(); 
ValueSet message = args.Request.Message;

Thank you.

---

If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 3

@Junjie Zhu - MSFT

Can't get the Appserviceconnnection to work in .Net 8 fulltrustprocess and UWP app  .

When the fulltrustprocess server starts with the call to Windows.ApplicationModel.FullTrustProcessLauncher.LaunchFullTrustProcessForCurrentAppAsync and tries to open the server the openasync always returns AppServiceUnavailable;

 

Here is the code in the main (fulltrustprocess)

program.cs

 

static async Task Main(string[] args)
{
AppServiceConversionServer appServiceServerManager = new AppServiceConversionServer();
 await appServiceServerManager.InitializeAppServiceAsync();
}

 

 AppServiceConversionServer.cs (fulltrustprocess)

namespace Desktop.FullTrustApp.AppService;
public class AppServiceConversionServer
{
 
public async Task InitializeAppServiceAsync()
{
AppserviceConnection = new AppServiceConnection
 {
     AppServiceName = "Desktop.FullTrustApp.AppService",
     PackageFamilyName = Windows.ApplicationModel.Package.Current.Id.FamilyName
 };
 AppServiceConnectionStatus status = await AppserviceConnection.OpenAsync();
  if (status == AppServiceConnectionStatus.Success)
 {
     AppserviceConnection.RequestReceived += OnRequestReceived;
     await Task.Delay(-1);
}
}
}

In the UWP App package.appxmanifest

 

<uap:Extension Category="windows.appService" EntryPoint=" Desktop.FullTrustApp.AppService.AppServiceConversionServer">
   <uap3:AppService Name="Desktop.FullTrustApp.AppService" uap4:SupportsMultipleInstances="true"/>
 </uap:Extension>

In the UWP client App, it starts the fulltrustprocess on some button click and tries to start the server connection for the client to communicate. 

await Windows.ApplicationModel.FullTrustProcessLauncher.LaunchFullTrustProcessForCurrentAppAsync();
 
 AppserviceConnection = new AppServiceConnection
 {
     AppServiceName = "Desktop.FullTrustApp.AppService",
     PackageFamilyName = Windows.ApplicationModel.Package.Current.Id.FamilyName
 };
 AppserviceConnection.RequestReceived += OnRequestReceived;
 
 
 for (int attempt = 1; attempt <= MaxConnectionRetries; attempt++)
 {
 
     status = await AppserviceConnection.OpenAsync();
     if (status == AppServiceConnectionStatus.Success)
     {
         break;
     }
     await Task.Delay(1000);
 }

In the fulltrustprocess server and UWP app client scenario , what is the correct way to make the connection work and send bi directional messages ? The learn documentation is confusing.