"Invalid request method" Exception

[ayberkcal]

I try to connect websocket server from flutter app and I faced exception. On the otherhand I can connect successfully with Postman and simple NodeJS code to websocket server.

Exception:
Unhandled Exception: WebSocketChannelException: WebSocketChannelException: HttpException: Invalid request method, uri = http://push.domain.com:0/XXXXXXXXXX

Minimum reproducable code:

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  var channel = WebSocketChannel.connect(
    Uri.parse('ws://push.domain.com/XXXXXXXXXX'),
  );

  /// Listen for all incoming data
  channel.stream.listen(
        (data) {
      print(data);
    },
    // onError: (error) => print(error),
  );

  runApp(const MyApp());
}

Stack Trace:

E/flutter ( 9522): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: WebSocketChannelException: WebSocketChannelException: HttpException: Invalid request method, uri = http://push.domain.com:0/XXXXXXXXXX
E/flutter ( 9522): #0      new IOWebSocketChannel._withoutSocket.<anonymous closure> (package:web_socket_channel/io.dart:98:24)
E/flutter ( 9522): #1      Stream.handleError.<anonymous closure> (dart:async/stream.dart:929:16)
E/flutter ( 9522): #2      _HandleErrorStream._handleError (dart:async/stream_pipe.dart:269:17)
E/flutter ( 9522): #3      _ForwardingStreamSubscription._handleError (dart:async/stream_pipe.dart:157:13)
E/flutter ( 9522): #4      _RootZone.runBinaryGuarded (dart:async/zone.dart:1598:10)
E/flutter ( 9522): #5      _BufferingStreamSubscription._sendError.sendError (dart:async/stream_impl.dart:358:15)
E/flutter ( 9522): #6      _BufferingStreamSubscription._sendError (dart:async/stream_impl.dart:376:7)
E/flutter ( 9522): #7      _BufferingStreamSubscription._addError (dart:async/stream_impl.dart:280:7)
E/flutter ( 9522): #8      _SyncStreamControllerDispatch._sendError (dart:async/stream_controller.dart:778:19)
E/flutter ( 9522): #9      _StreamController._addError (dart:async/stream_controller.dart:656:7)
E/flutter ( 9522): #10     _RootZone.runBinaryGuarded (dart:async/zone.dart:1598:10)
E/flutter ( 9522): #11     _BufferingStreamSubscription._sendError.sendError (dart:async/stream_impl.dart:358:15)
E/flutter ( 9522): #12     _BufferingStreamSubscription._sendError (dart:async/stream_impl.dart:376:7)
E/flutter ( 9522): #13     _BufferingStreamSubscription._addError (dart:async/stream_impl.dart:280:7)
E/flutter ( 9522): #14     _SyncStreamControllerDispatch._sendError (dart:async/stream_controller.dart:778:19)
E/flutter ( 9522): #15     _StreamController._addError (dart:async/stream_controller.dart:656:7)
E/flutter ( 9522): #16     new Stream.fromFuture.<anonymous closure> (dart:async/stream.dart:251:18)
E/flutter ( 9522): #17     _RootZone.runBinary (dart:async/zone.dart:1658:54)
E/flutter ( 9522): #18     _FutureListener.handleError (dart:async/future_impl.dart:162:22)
E/flutter ( 9522): #19     Future._propagateToListeners.handleError (dart:async/future_impl.dart:778:47)
E/flutter ( 9522): #20     Future._propagateToListeners (dart:async/future_impl.dart:799:13)
E/flutter ( 9522): #21     Future._completeError (dart:async/future_impl.dart:574:5)
E/flutter ( 9522): #22     Future._asyncCompleteError.<anonymous closure> (dart:async/future_impl.dart:665:7)
E/flutter ( 9522): #23     _microtaskLoop (dart:async/schedule_microtask.dart:40:21)
E/flutter ( 9522): #24     _startMicrotaskLoop (dart:async/schedule_microtask.dart:49:5)
E/flutter ( 9522): 

Flutter doctor summary:

Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 3.3.8, on Microsoft Windows [Version 10.0.19043.2130], locale en-US)
[√] Android toolchain - develop for Android devices (Android SDK version 30.0.3)                 
[√] Chrome - develop for the web                                                                                                                                             
[!] Visual Studio - develop for Windows (Visual Studio Enterprise 2022 17.3.0)                                                                                               
    X Visual Studio is missing necessary components. Please re-run the Visual Studio installer for the "Desktop development with C++" workload, and include these components:
        MSVC v142 - VS 2019 C++ x64/x86 build tools                                                                                                                          
         - If there are multiple build tool versions available, install the latest                                                                                           
        C++ CMake tools for Windows                                                                                                                                          
        Windows 10 SDK                                                                                                                                                       
[√] Android Studio (version 2021.3)                                                                                                                                          
[√] IntelliJ IDEA Ultimate Edition (version 2022.2)                                                                                                                          
[√] VS Code (version 1.73.0)                                                                                                                                                 
[√] Connected device (4 available)                                                                                                                                           
[√] HTTP Host Availability                                                                                                                                                   

! Doctor found issues in 1 category.

[ayberkcal]

WebSocketChannel connect with lower case sec-websocket-version header. However it is not respect to RFC 6455. RFC said header must be "Sec-WebSocket-Version". I think this is major issue about compatability. Also there is a lots of connection issue about that problem.