unsupported_protocol(handshake_client.cc:697)

[parmkub]

before upgrade flutter is version 3 . mailer error UNSUPPORTED_PROTOCOL(handshake_client.cc:697)
#0 _SecureFilterImpl._handshake(dart:io-patch/secure_socket_patch.dart:99:46)
#1 _SecureFilterImpl._handshake(dart:io-patch/secure_socket_patch.dart:99:46)
#2 RawSecureSocket.secureHandshake(dart:io/secure_socket.dart:911:54)
#3 RawSecureSocket._tryFilter(dart:io/secure_socket.dart:1040:19)

How to fix it. thank

[close2]

This is not enough information.

Please enable debugging and provide the log output.
(Hide your password)

    Logger.root.level = Level.ALL;
    Logger.root.onRecord.listen((LogRecord rec) {
      print('${rec.level.name}: ${rec.time}: ${rec.message}');
    });