UIMessage communication. Single instancing for server and re-connection mechanism on suspension.

Wino.Server/App.xaml.cs

@@ -1,18 +1,70 @@
-using System.Windows;
+using System.Threading;
+using System.Windows;
 using H.NotifyIcon;
 
 namespace Wino.Server
 {
+    /// <summary>
+    /// Single instance Wino Server.
+    /// Instancing is done using Mutex.
+    /// App will not start if another instance is already running.
+    /// App will let running server know that server execution is triggered, which will
+    /// led server to start new connection to requesting UWP app.
+    /// </summary>
     public partial class App : Application
     {
+        private const string WinoServerAppName = "Wino.Server";
+        private const string WinoServerActiatedName = "Wino.Server.Activated";
+
         private TaskbarIcon? notifyIcon;
+        private static Mutex _mutex = null;
+        private EventWaitHandle _eventWaitHandle;
 
         protected override void OnStartup(StartupEventArgs e)
         {
-            base.OnStartup(e);
+            bool isCreatedNew;
 
-            notifyIcon = (TaskbarIcon)FindResource("NotifyIcon");
-            notifyIcon.ForceCreate(enablesEfficiencyMode: true);
+            _mutex = new Mutex(true, WinoServerAppName, out isCreatedNew);
+            _eventWaitHandle = new EventWaitHandle(false, EventResetMode.AutoReset, WinoServerActiatedName);
+
+            if (isCreatedNew)
+            {
+                // Spawn a thread which will be waiting for our event
+                var thread = new Thread(() =>
+                {
+                    while (_eventWaitHandle.WaitOne())
+                    {
+                        if (notifyIcon == null) return;
+
+                        Current.Dispatcher.BeginInvoke(() =>
+                        {
+                            if (notifyIcon.DataContext is TrayIconViewModel trayIconViewModel)
+                            {
+                                trayIconViewModel.Reconnect();
+                            }
+                        });
+                    }
+                });
+
+                // It is important mark it as background otherwise it will prevent app from exiting.
+                thread.IsBackground = true;
+
+                thread.Start();
+
+                base.OnStartup(e);
+
+                // Create taskbar icon for the new server.
+                notifyIcon = (TaskbarIcon)FindResource("NotifyIcon");
+                notifyIcon.ForceCreate(enablesEfficiencyMode: true);
+            }
+            else
+            {
+                // Notify other instance so it could bring itself to foreground.
+                _eventWaitHandle.Set();
+
+                // Terminate this instance.
+                Shutdown();
+            }
         }
 
         protected override void OnExit(ExitEventArgs e)