[multicast_dns] Allow handling socket errors

packages/multicast_dns/CHANGELOG.md

@@ -1,6 +1,7 @@
-## NEXT
+## 0.3.2+8
 
 * Updates minimum supported SDK version to Flutter 3.22/Dart 3.4.
+* Adds `onSocketError` to `MDnsClient.start`.
 
 ## 0.3.2+7
 

packages/multicast_dns/lib/multicast_dns.dart

@@ -84,13 +84,19 @@ class MDnsClient {
   /// for the mDNS query. If not provided, defaults to either `224.0.0.251` or
   /// or `FF02::FB`.
   ///
+  /// On socket errors, the [onSocketError] handler is called with the error
+  /// object and possibly a stack trace. The [onSocketError] callback must be of
+  /// type `void Function(Object error)` or
+  /// `void Function(Object error, StackTrace)`.
+  ///
   /// Subsequent calls to this method are ignored while the mDNS client is in
   /// started state.
   Future<void> start({
     InternetAddress? listenAddress,
     NetworkInterfacesFactory? interfacesFactory,
     int mDnsPort = mDnsPort,
     InternetAddress? mDnsAddress,
+    Function? onSocketError,
   }) async {
     listenAddress ??= InternetAddress.anyIPv4;
     interfacesFactory ??= allInterfacesFactory;
@@ -152,7 +158,10 @@ class MDnsClient {
       // Join multicast on this interface.
       incoming.joinMulticast(_mDnsAddress!, interface);
     }
-    incoming.listen((RawSocketEvent event) => _handleIncoming(event, incoming));
+    incoming.listen(
+      (RawSocketEvent event) => _handleIncoming(event, incoming),
+      onError: onSocketError,
+    );
     _started = true;
     _starting = false;
   }

packages/multicast_dns/lib/src/lookup_resolver.dart

@@ -48,7 +48,7 @@ class LookupResolver {
     return controller.stream;
   }
 
-  /// Parses [ResoureRecord]s received and delivers them to the appropriate
+  /// Parses [ResourceRecord]s received and delivers them to the appropriate
   /// listener(s) added via [addPendingRequest].
   void handleResponse(List<ResourceRecord> response) {
     for (final ResourceRecord r in response) {

packages/multicast_dns/test/client_test.dart

@@ -158,26 +158,51 @@ void main() {
       });
     }
   });
+
+  test('Reports socket errors', () async {
+    final FakeRawDatagramSocket datagramSocket = FakeRawDatagramSocket();
+    final MDnsClient client = MDnsClient(rawDatagramSocketFactory:
+        (dynamic host, int port,
+            {bool reuseAddress = true,
+            bool reusePort = true,
+            int ttl = 1}) async {
+      return datagramSocket;
+    });
+
+    final Completer<void> errorCompleter = Completer<void>();
+
+    await client.start(onError: (Object e, StackTrace stacktrace) {
+      expect(e, 'Hello world');
+      errorCompleter.complete();
+    });
+
+    datagramSocket.controller.addError('Hello world');
+    await errorCompleter.future;
+  });
 }
 
 class FakeRawDatagramSocket extends Fake implements RawDatagramSocket {
   @override
   InternetAddress address = InternetAddress.anyIPv4;
 
+  final StreamController<RawSocketEvent> controller =
+      StreamController<RawSocketEvent>();
+
   @override
   StreamSubscription<RawSocketEvent> listen(
       void Function(RawSocketEvent event)? onData,
       {Function? onError,
       void Function()? onDone,
       bool? cancelOnError}) {
-    return const Stream<RawSocketEvent>.empty().listen(onData,
+    return controller.stream.listen(onData,
         onError: onError, cancelOnError: cancelOnError, onDone: onDone);
   }
 
   bool closed = false;
 
   @override
   void close() {
+    controller.close();
     closed = true;
   }