fix(lib): add message checks and improve exceptions

example/lib/main.dart

@@ -53,15 +53,15 @@ class MyApp extends StatelessWidget {
                       ),
                       if (service.currentDeviceInfo != null)
                         Text(
-                          'Device Name: ${service.currentDeviceInfo!.displayName}\n'
+                          'Device Name: ${service.currentDeviceInfo!.displayName}'
-                          '${Platform.isIOS ? 'Device ID: ${service.currentDeviceInfo!.id}' : ''}',
+                          '${Platform.isIOS ? '\nDevice ID: ${service.currentDeviceInfo!.id}' : ''}',
                         ),
                       if (Platform.isIOS)
                         Text(
                           'You are ${service.isIOSBrowser ? 'going to find your friend' : 'waiting for another user to connect'}',
                         ),
                       Text(
-                        'Communication channel state: ${service.communicationChannelState.name.toUpperCase()}',
+                        'Communication channel state: ${service.communicationChannelState.previewName}',
                       )
                     ],
                   ),
@@ -172,6 +172,16 @@ enum AppState {
   }
 }
 
+extension on CommunicationChannelState {
+  String get previewName {
+    return switch (this) {
+      CommunicationChannelState.notConnected => 'Not connected',
+      CommunicationChannelState.loading => 'Connecting',
+      CommunicationChannelState.connected => 'Connected',
+    };
+  }
+}
+
 class AppService extends ChangeNotifier {
   late final _nearbyService = NearbyService.getInstance()
     ..communicationChannelState.addListener(notifyListeners);
@@ -187,6 +197,12 @@ class AppService extends ChangeNotifier {
   StreamSubscription? peersSubscription;
   StreamSubscription? connectedDeviceSubscription;
 
+  @override
+  void dispose() {
+    stopListeningAll();
+    super.dispose();
+  }
+
   CommunicationChannelState get communicationChannelState {
     return _nearbyService.communicationChannelState.value;
   }
@@ -328,7 +344,7 @@ class AppService extends ChangeNotifier {
           final wasConnected = connectedDevice?.status.isConnected ?? false;
           final nowConnected = event?.status.isConnected ?? false;
           if (wasConnected && !nowConnected) {
-            restart();
+            stopListeningAll();
             return;
           }
           connectedDevice = event;
@@ -358,7 +374,7 @@ class AppService extends ChangeNotifier {
   Future<void> startCommunicationChannel({
     ValueChanged<ReceivedNearbyMessage>? listener,
   }) async {
-    final eventListener = NearbyServiceStreamListener<ReceivedNearbyMessage>(
+    final eventListener = NearbyServiceStreamListener(
       onCreated: (_) {
         updateState(AppState.communicationChannelCreated);
       },
@@ -366,7 +382,7 @@ class AppService extends ChangeNotifier {
         listener?.call(event);
       },
       onError: (e, [StackTrace? s]) {
-        restart();
+        stopListeningAll();
       },
     );
 
@@ -396,17 +412,15 @@ class AppService extends ChangeNotifier {
         print(e);
       }
     } finally {
-      await restart();
+      await stopListeningAll();
     }
     notifyListeners();
   }
 
-  Future<void> restart() async {
+  Future<void> stopListeningAll() async {
     await stopListeningConnectedDevice();
     await stopListeningPeers();
     await stopDiscovery();
-
-    await discover();
   }
 
   void updateState(AppState state, {bool shouldNotify = true}) {
@@ -768,7 +782,7 @@ class _ConnectedSocketBodyState extends State<_ConnectedSocketBody> {
         if (device == null) {
           return Center(
             child: _ActionButton(
-              onTap: service.restart,
+              onTap: service.stopListeningAll,
               title: 'Restart',
             ),
           );

lib/src/models/nearby_message.dart

@@ -12,6 +12,13 @@ abstract class NearbyMessage {
 
   final String value;
 
+  ///
+  /// Checks if [value] is not empty
+  ///
+  bool get isValid {
+    return value.isNotEmpty;
+  }
+
   @override
   bool operator ==(Object other) =>
       identical(this, other) ||

lib/src/platforms/android/socket_service/nearby_socket_service.dart

@@ -27,6 +27,7 @@ class NearbySocketService {
 
   String? _connectedDeviceId;
   WebSocket? _socket;
+  HttpServer? _server;
   StreamSubscription<ReceivedNearbyMessage>? _messagesSubscription;
 
   ///
@@ -72,21 +73,25 @@ class NearbySocketService {
   /// Add [OutgoingNearbyMessage]'s JSON representation to [_socket].
   ///
   Future<bool> send(OutgoingNearbyMessage message) async {
-    if (_socket != null && message.receiver.id == _connectedDeviceId) {
+    if (message.isValid) {
-      final sender = await _manager.getCurrentDeviceInfo();
+      if (_socket != null && message.receiver.id == _connectedDeviceId) {
-      if (sender != null) {
+        final sender = await _manager.getCurrentDeviceInfo();
-        _socket!.add(
+        if (sender != null) {
-          jsonEncode(
+          _socket!.add(
-            {
+            jsonEncode(
-              'message': message.value,
+              {
-              'sender': sender.toJson(),
+                'message': message.value,
-            },
+                'sender': sender.toJson(),
-          ),
+              },
-        );
+            ),
+          );
+        }
+        return true;
       }
-      return true;
+      return false;
+    } else {
+      throw NearbyServiceException.invalidMessage(message.value);
     }
-    return false;
   }
 
   ///
@@ -96,8 +101,12 @@ class NearbySocketService {
     try {
       await _messagesSubscription?.cancel();
       _messagesSubscription = null;
+      _socket?.close();
       _socket = null;
+      _server?.close(force: true);
+      _server = null;
       _connectedDeviceId = null;
+      state.value = CommunicationChannelState.notConnected;
       return true;
     } catch (e) {
       return false;
@@ -142,11 +151,11 @@ class NearbySocketService {
     required int port,
     ValueChanged<HttpRequest>? serverListener,
   }) async {
-    final httpServer = await _network.startServer(
+    _server = await _network.startServer(
       ownerIpAddress: info.ownerIpAddress,
       port: port,
     );
-    httpServer?.listen(
+    _server?.listen(
       (request) async {
         serverListener?.call(request);
         final isPing = await _pingManager.checkPing(request);
@@ -156,7 +165,7 @@ class NearbySocketService {
           return;
         }
 
-        if (request.uri.path == '/ws') {
+        if (request.uri.path == _Urls.ws) {
           _socket = await WebSocketTransformer.upgrade(request);
           _createSocketSubscription(socketListener);
         } else {

lib/src/platforms/android/socket_service/network.dart

@@ -5,6 +5,10 @@ class _Protocols {
   static const ws = 'ws://';
 }
 
+class _Urls {
+  static const ws = '/ws';
+}
+
 class NearbyServiceNetwork {
   final _httpClient = HttpClient();
   final _random = Random();
@@ -20,7 +24,7 @@ class NearbyServiceNetwork {
       final response = await request.close();
       return response;
     } catch (e) {
-      Logger.error('Server is unreachable');
+      Logger.error('Server is unreachable: $e');
       return null;
     }
   }
@@ -37,7 +41,7 @@ class NearbyServiceNetwork {
     required int port,
   }) async {
     try {
-      final url = 'ws://$ownerIpAddress:$port';
+      final url = '${_Protocols.ws}$ownerIpAddress:$port';
       Logger.debug('Starting server on $url');
       var server = await HttpServer.bind(
         ownerIpAddress,
@@ -47,8 +51,7 @@ class NearbyServiceNetwork {
       Logger.info('Server running on $url');
       return server;
     } catch (e) {
-      Logger.error('Error starting socket: $e');
+      throw NearbyServiceException('Error starting socket: $e');
-      return null;
     }
   }
 
@@ -58,14 +61,14 @@ class NearbyServiceNetwork {
   }) async {
     try {
       final connectionId = _random.nextInt(1000) + 100;
-      final url = '${_Protocols.ws}$ownerIpAddress:$port/ws?as=$connectionId';
+      final url =
+          '${_Protocols.ws}$ownerIpAddress:$port${_Urls.ws}?as=$connectionId';
       Logger.debug('Connecting to $url');
       final socket = await WebSocket.connect(url);
       Logger.info('Connected to $url');
       return socket;
     } catch (e) {
-      Logger.error('Error connecting to server: $e');
+      throw NearbyServiceException('Error connecting to server: $e');
-      return null;
     }
   }
 }

lib/src/platforms/ios/nearby_ios_service.dart

@@ -201,6 +201,7 @@ class NearbyIOSService extends NearbyService {
   FutureOr<bool> endCommunicationChannel() async {
     await _messagesSubscription?.cancel();
     _messagesSubscription = null;
+    _state.value = CommunicationChannelState.notConnected;
     Logger.debug('Communication channel was cancelled');
     return true;
   }
@@ -211,7 +212,10 @@ class NearbyIOSService extends NearbyService {
   ///
   @override
   Future<bool> send(OutgoingNearbyMessage message) {
-    return NearbyServiceIOSPlatform.instance.send(message);
+    if (message.isValid) {
+      return NearbyServiceIOSPlatform.instance.send(message);
+    }
+    throw NearbyServiceException.invalidMessage(message.value);
   }
 
   ///
@@ -242,7 +246,7 @@ class NearbyIOSService extends NearbyService {
     if (value) {
       Logger.info(onSuccess);
     } else {
-      Logger.error(onError);
+      throw NearbyServiceException(onError);
     }
   }
 

lib/src/types/communication_channel_data.dart

@@ -28,7 +28,7 @@ class NearbyCommunicationChannelData {
   ///
   /// Listener for message stream changes.
   ///
-  final NearbyServiceStreamListener<ReceivedNearbyMessage> eventListener;
+  final NearbyServiceStreamListener eventListener;
 
   ///
   /// Android-specific connection data.

lib/src/types/nearby_service_stream_listener.dart

@@ -1,11 +1,12 @@
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';
+import 'package:nearby_service/nearby_service.dart';
 
 ///
 /// Stream Subscription Listener.
 ///
-class NearbyServiceStreamListener<T> {
+class NearbyServiceStreamListener {
   ///
   /// It is required to pass the [onData] parameter to process the
   /// data that came through the stream.
@@ -18,8 +19,8 @@ class NearbyServiceStreamListener<T> {
     this.cancelOnError,
   });
 
-  final ValueChanged<T> onData;
+  final ValueChanged<ReceivedNearbyMessage> onData;
-  final ValueChanged<StreamSubscription<T>>? onCreated;
+  final ValueChanged<StreamSubscription<ReceivedNearbyMessage>>? onCreated;
   final VoidCallback? onDone;
   final void Function(Object, [StackTrace])? onError;
   final bool? cancelOnError;

lib/src/utils/exception.dart

@@ -30,5 +30,11 @@ class NearbyServiceException implements Exception {
     );
   }
 
+  factory NearbyServiceException.invalidMessage(String value) {
+    return NearbyServiceException(
+      'The message="$value" is not valid',
+    );
+  }
+
   final Object? error;
 }