performance issue on mac os x when using localhost in url

[ErikGrimes]

A simple request like getting the string "hello" using the http package from a shelf server running on the same host takes an unusually long time (5 seconds) when the url refers to localhost on my mac. The same connection takes less than 5 milliseconds on Chrome. The request takes less than 100 ms when the url uses 127.0.0.1 instead of localhost. I repeated the test on an Ubuntu Linux machine using localhost and it behaves as expected.

client

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

main(List<String> args) async {

    var client = new http.Client();

    Stopwatch sw = new Stopwatch();
    sw.start();

    var response = await client.get(Uri.parse("http://localhost:10080"));

    sw.stop();

    print('response received ${sw.elapsedMilliseconds}');
    client.close();



}

server

import 'dart:io';
import 'package:shelf/shelf.dart';
import 'package:shelf/shelf_io.dart';

main(List<String> args) async {

  var handler = (Request r){
    return new Response.ok("hello");
  } ;

  var server = await serve(const Pipeline()
      .addMiddleware(logRequests())
      .addHandler(handler),  InternetAddress.ANY_IP_V4, 10080);

  print('Serving at http://${server.address.host}:${server.port}');

sdk: 1.19.1
mac os x: 10.11.6
http: 0.11.3+9
shelf: 0.6.5+3

[ErikGrimes]

This appears to be related to Mac OS X and not Dart. I'm seeing the same connection delay to "localhost" from Java.