Flutter app: cannot get HTTP response from server with client certificates enabled

Question

I try to send HTTP GET request to a server with a "client certificate" enabled in my Flutter app. The server allows client certificates because some of the clients (Desktop apps) use certificates for authorization with this server.

Expected results: HTTP response

Actual results: The GET request receives in the server but the Dart's HTTP GET method throws a ClientException with an empty message before a response is received.

Server configuration and details: OS: Windows Host: IIS HTTP version: 1.1 Minimum TLS version: 1.2 Runtime: ASP .NET Core 5

If I disable "client certificate" authorization on the server everything works fine. But this is not a good solution for me.

BTW: I manage to make a request and get a response via other in other platforms to the same endpoint in this server without any problem! I try C# console app, Xamrin Forms app and Postman and this issue exists only in Flutter!

Update: I still don't have a solution for this one. At your request I attached my code snipped, it's a simple HTTP service. Nothing fancy. And the error I get is ClientException without a message.

import 'dart:async';
import 'dart:convert';
import 'dart:io';

import 'package:http/http.dart' as http;
import 'package:retry/retry.dart';

import '../models/app_exception.dart';
import 'logs_service.dart';

class HttpService {
  final _timeoutDuration = Duration(minutes: 1);
  final _retryOptions = RetryOptions(maxAttempts: 3);

  final _headers = {
    HttpHeaders.acceptHeader: 'application/json; charset=UTF-8',
    HttpHeaders.pragmaHeader: 'no-cache',
    HttpHeaders.contentTypeHeader: 'application/json; charset=UTF-8',
    HttpHeaders.acceptCharsetHeader: 'UTF-8',
  };

  Future<dynamic> get({
    required String url,
    String? authorizationToken,
    Map<String, String>? args,
    String? basicAuthUsername,
    String? basicAuthPassword,
  }) {
    return _retryOptions.retry(
      () => _get(
        url,
        authorizationToken,
        args,
        basicAuthUsername,
        basicAuthPassword,
      ).timeout(_timeoutDuration),
      retryIf: (e) => e is NetworkException,
    );
  }

  Future<dynamic> _get(
    String baseUrl,
    String? authorizationToken,
    Map<String, String>? args,
    String? basicAuthUsername,
    String? basicAuthPassword,
  ) async {
    try {
      var responseJson;

      final headers = Map<String, String>.from(_headers);

      if (authorizationToken != null) {
        headers[HttpHeaders.authorizationHeader] = authorizationToken;
      }
      if (basicAuthUsername != null && basicAuthPassword != null) {
        headers[HttpHeaders.authorizationHeader] =
            _getBasicAuthStr(basicAuthUsername, basicAuthPassword);
      }

      final argsStr = args.convertToQueryString;

      final url = Uri.parse('$baseUrl$argsStr');

      try {
        final response = await http.get(
          url,
          headers: headers,
        );

        logger.info(
            text:
                'GET | url: $url | response status code: ${response.statusCode}');

        responseJson = _returnResponse(response.body, response.statusCode);
      } on SocketException {
        throw NetworkException('No Internet connection');
      }
      return responseJson;
    } catch (e) {
      logger.error(error: e, text: 'GET | error | url: $baseUrl');
      throw e;
    }
  }

  
  dynamic _returnResponse(String responseBody, int statusCode) {
    if (statusCode >= 200 && statusCode < 300) {
      final responseJson = responseBody.isNotEmpty
          ? json.decode(responseBody)
          : Map<String, dynamic>();
      return responseJson;
    }

    switch (statusCode) {
      case 400:
        throw BadRequestException(responseBody);
      case 401:
        throw UnauthorizedException(responseBody);
      case 403:
        switch (responseBody) {
          case '\"DeviceUnregistered\"':
            throw DeviceUnregisteredException(responseBody);
          case '\"NoAppLicense\"':
            throw NoAppLicenseException(responseBody);
          case '\"InvitationNotFound\"':
            throw InvitationNotFoundException(responseBody);
          case '\"InvitationExpired\"':
            throw InvitationExpiredException(responseBody);
          case '\"DeviceAlreadyRegistered\"':
            throw DeviceAlreadyRegisteredException(responseBody);
        }
        throw ForbiddenException(responseBody);
      case 404:
        throw NotFoundException(responseBody);
      case 500:
      case 501:
      case 502:
      case 503:
        throw ServerErrorException(
            'status code: $statusCode | body: $responseBody');
      default:
        throw GeneralHttpErrorException(
            'Error occurred while communication with server | Status code: $statusCode | body: $responseBody');
    }
  }

  String _getBasicAuthStr(String userName, String password) =>
      'Basic ' + base64Encode(utf8.encode('$userName:$password'));
}

extension StringMapeExtension on Map<String, String?>? {
  String get convertToQueryString {
    String query = '';
    if (this == null) {
      return query;
    }
    for (MapEntry e in this!.entries) {
      query += '&${e.key}=${e.value}';
    }
    return ('?${query.substring(1)}');
  }
}