Why I cannot start the connection? I use longpolling transport, this is my log
flutter: FINEST: 2021-12-03 14:01:43.050495: (LongPolling transport) polling: http://myserver/signalr?id=BXLNU7zyRfpM23oX5u_g5A&_=2021-12-03 14:01:43.050220 flutter: SEVERE: 2021-12-03 14:01:43.066492: Failed to start the transport 'HttpTransportType.LongPolling': type 'Null' is not a subtype of type 'String' in type cast flutter: SEVERE: 2021-12-03 14:01:43.067837: Failed to start the connection: Unable to connect to the server with any of the available transports. HttpTransportType.ServerSentEvents failed: Skipping transport 'HttpTransportType.ServerSentEvents' because it was disabled by the client. HttpTransportType.LongPolling failed: type 'Null' is not a subtype of type 'String' in type cast flutter: FINER: 2021-12-03 14:01:43.068564: HubConnection failed to start successfully because of error 'Unable to connect to the server with any of the available transports. HttpTransportType.ServerSentEvents failed: Skipping transport 'HttpTransportType.ServerSentEvents' because it was disabled by the client. HttpTransportType.LongPolling failed: type 'Null' is not a subtype of type 'String' in type cast'. Application finished.
Why I cannot start the connection? I use longpolling transport, this is my log
flutter: FINEST: 2021-12-03 14:01:43.050495: (LongPolling transport) polling: http://myserver/signalr?id=BXLNU7zyRfpM23oX5u_g5A&_=2021-12-03 14:01:43.050220 flutter: SEVERE: 2021-12-03 14:01:43.066492: Failed to start the transport 'HttpTransportType.LongPolling': type 'Null' is not a subtype of type 'String' in type cast flutter: SEVERE: 2021-12-03 14:01:43.067837: Failed to start the connection: Unable to connect to the server with any of the available transports. HttpTransportType.ServerSentEvents failed: Skipping transport 'HttpTransportType.ServerSentEvents' because it was disabled by the client. HttpTransportType.LongPolling failed: type 'Null' is not a subtype of type 'String' in type cast flutter: FINER: 2021-12-03 14:01:43.068564: HubConnection failed to start successfully because of error 'Unable to connect to the server with any of the available transports. HttpTransportType.ServerSentEvents failed: Skipping transport 'HttpTransportType.ServerSentEvents' because it was disabled by the client. HttpTransportType.LongPolling failed: type 'Null' is not a subtype of type 'String' in type cast'. Application finished.