Replace socket approach with native Windows mutex.

lib/desktop/single_instance.dart

@@ -1,68 +0,0 @@
-import 'dart:io';
-import 'package:logging/logging.dart';
-import 'package:path/path.dart' as path;
-
-import 'package:path_provider/path_provider.dart';
-import 'package:window_manager/window_manager.dart';
-
-const _lockFileName = 'lockfile';
-const _pingMessage = 'YA-PING';
-const _pongMessage = 'YA-PONG';
-
-final log = Logger('single_instance');
-
-void _startServer(File lockfile) async {
-  final socket = await ServerSocket.bind(InternetAddress.loopbackIPv4, 0);
-  lockfile.writeAsString('${socket.port}');
-
-  log.info('Lock file and socket created.');
-  socket.listen((client) {
-    client.listen((data) async {
-      final message = String.fromCharCodes(data);
-      if (message == _pingMessage) {
-        log.info('Got incomming connection');
-
-        if (!await WindowManager.instance.isMinimized()) {
-          // Causes the window to be brought to the front.
-          await WindowManager.instance.setAlwaysOnTop(true);
-          await WindowManager.instance.setAlwaysOnTop(false);
-        } else {
-          await WindowManager.instance.restore();
-        }
-
-        // This doesn't seem to always work
-        await WindowManager.instance.focus();
-        client.write(_pongMessage);
-      }
-      client.close();
-    }, cancelOnError: true);
-  });
-}
-
-Future<void> ensureSingleInstance() async {
-  final appSupport = await getApplicationSupportDirectory();
-  final lockfile = File(path.join(appSupport.path, _lockFileName));
-  log.info('Lock file: $lockfile');
-
-  if (await lockfile.exists()) {
-    try {
-      final port = int.parse(await lockfile.readAsString());
-      final client = await Socket.connect(InternetAddress.loopbackIPv4, port);
-      client.write(_pingMessage);
-      client.listen((data) async {
-        final message = String.fromCharCodes(data);
-        await client.close();
-        if (message == _pongMessage) {
-          log.info('Other application instance already running, exit.');
-          exit(0);
-        }
-      }, cancelOnError: true);
-    } on Exception {
-      // No server listening on the port, or bad data in the file
-      await lockfile.delete();
-      _startServer(lockfile);
-    }
-  } else {
-    _startServer(lockfile);
-  }
-}

lib/main.dart

@@ -6,7 +6,6 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import 'package:logging/logging.dart';
 import 'package:window_manager/window_manager.dart';
-import 'package:yubico_authenticator/desktop/single_instance.dart';
 
 import 'app/app.dart';
 import 'app/views/main_page.dart';
@@ -20,9 +19,6 @@ final log = Logger('main');
 void main() async {
   _initLogging(Level.INFO);
   WidgetsFlutterBinding.ensureInitialized();
-  if (Platform.isWindows) {
-    await ensureSingleInstance();
-  }
   await windowManager.ensureInitialized();
 
   // Either use the _YKMAN_EXE environment variable, or look relative to executable.

macos/Flutter/GeneratedPluginRegistrant.swift

@@ -5,12 +5,10 @@
 import FlutterMacOS
 import Foundation
 
-import path_provider_macos
 import shared_preferences_macos
 import window_manager
 
 func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
-  PathProviderPlugin.register(with: registry.registrar(forPlugin: "PathProviderPlugin"))
   SharedPreferencesPlugin.register(with: registry.registrar(forPlugin: "SharedPreferencesPlugin"))
   WindowManagerPlugin.register(with: registry.registrar(forPlugin: "WindowManagerPlugin"))
 }

pubspec.lock

@@ -352,27 +352,6 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.8.0"
-  path_provider:
-    dependency: "direct main"
-    description:
-      name: path_provider
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.8"
-  path_provider_android:
-    dependency: transitive
-    description:
-      name: path_provider_android
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.11"
-  path_provider_ios:
-    dependency: transitive
-    description:
-      name: path_provider_ios
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.7"
   path_provider_linux:
     dependency: transitive
     description:
@@ -380,13 +359,6 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "2.1.5"
-  path_provider_macos:
-    dependency: transitive
-    description:
-      name: path_provider_macos
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.5"
   path_provider_platform_interface:
     dependency: transitive
     description:

pubspec.yaml

@@ -37,7 +37,6 @@ dependencies:
 
   async: ^2.8.2
   logging: ^1.0.2
-  path_provider: ^2.0.8
   shared_preferences: ^2.0.12
   flutter_riverpod: ^1.0.0
   json_annotation: ^4.4.0

windows/runner/win32_window.cpp

@@ -107,6 +107,28 @@ bool Win32Window::CreateAndShow(const std::wstring& title,
                                 const Size& size) {
   Destroy();
 
+  // Attempt to create a mutex to enforce single instance.
+  CreateMutex(NULL, TRUE, L"com.yubico.authenticator.mutex");
+  if (GetLastError() == ERROR_ALREADY_EXISTS) {
+      HWND handle=FindWindowA(NULL, "Yubico Authenticator");
+      WINDOWPLACEMENT place = { sizeof(WINDOWPLACEMENT) };
+      GetWindowPlacement(handle, &place);
+      switch(place.showCmd) {
+          case SW_SHOWMAXIMIZED:
+              ShowWindow(handle, SW_SHOWMAXIMIZED);
+              break;
+          case SW_SHOWMINIMIZED:
+              ShowWindow(handle, SW_RESTORE);
+              break;
+          default:
+              ShowWindow(handle, SW_NORMAL);
+              break;
+      }
+      SetWindowPos(0, HWND_TOP, 0, 0, 0, 0, SWP_SHOWWINDOW | SWP_NOSIZE | SWP_NOMOVE);
+      SetForegroundWindow(handle);
+      return 0;
+  }
+
   const wchar_t* window_class =
       WindowClassRegistrar::GetInstance()->GetWindowClass();