How to catch SocketException using the http library?

Question

This problem has already been pointed out by others (like here). Althought I may have understood the cause, I still haven't found a solution when using the higher-level http library. For example:

import 'package:http/http.dart';

// yes, pwd is String, it's just a test...
Future<Response> login(String user, String pwd) {
  final authHeader = encodeBasicCredentials(user, pwd);
  return get(
    'http://192.168.0.100:8080/login',
    headers: <String, String>{
    HttpHeaders.AUTHORIZATION: authHeader,
    },
  ));
}

I can't find a way to catch a SocketException that is thrown, for example, if the host can't be reached (in my case, wrong host ip). I have tried wrapping the await in try/catch, or using Future.catchError.

This is a stacktrace of the exception:

[ERROR:topaz/lib/tonic/logging/dart_error.cc(16)] Unhandled exception:
E/flutter ( 4036): SocketException: OS Error: Connection refused, errno = 111, address = 192.168.0.100, port = 35588
E/flutter ( 4036): #0      IOClient.send (package:http/src/io_client.dart:30:23)
E/flutter ( 4036): <asynchronous suspension>
E/flutter ( 4036): #1      BaseClient._sendUnstreamed (package:http/src/base_client.dart:171:38)
E/flutter ( 4036): <asynchronous suspension>
E/flutter ( 4036): #2      BaseClient.get (package:http/src/base_client.dart:34:5)
E/flutter ( 4036): #3      get.<anonymous closure> (package:http/http.dart:47:34)
E/flutter ( 4036): #4      _withClient (package:http/http.dart:167:20)
E/flutter ( 4036): <asynchronous suspension>
E/flutter ( 4036): #5      get (package:http/http.dart:47:3)

Answer 1

You can check the type of the exception and treat it accordingly something like:

Future<Response> login(String user, String pwd) async {
  final String authHeader = encodeBasicCredentials(user, pwd);
  try {
    return await get(
        'http://192.168.0.100:8080/login',
        headers: {
          HttpHeaders.AUTHORIZATION: authHeader,
        },
      );
  } catch (e) {
    if(e is SocketException){
       //treat SocketException
       print("Socket exception: ${e.toString()}");
    }
    else if(e is TimeoutException){
       //treat TimeoutException
       print("Timeout exception: ${e.toString()}");
    }
    else print("Unhandled exception: ${e.toString()}");
  }
}

Probly better off making an error handler lib, so you can just call a function like handleException(e); on the catch block.

Answer 2

You can change login to be async so that you can await the response. That allows you to catch the exception (and, for example, return null instead of the Response).

Future<Response> login(String user, String pwd) async {
  final String authHeader = encodeBasicCredentials(user, pwd);
  try {
    return await get(
        'http://192.168.0.100:8080/login',
        headers: {
          HttpHeaders.AUTHORIZATION: authHeader,
        },
      );
  } catch (e) {
    print(e);
    return null;
  }
}