Change '127.0.0.1' to 'localhost' to support both IPv4 and IPv6 envs.

test/http_body_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:io';
 import 'dart:convert';
 
 import 'package:http_server/http_server.dart';
 import 'package:unittest/unittest.dart';
 
 void testHttpClientResponseBody() {
   void test(String mimeType,
             List<int> content,
             dynamic expectedBody,
             String type,
             [bool shouldFail = false]) {
-    HttpServer.bind("127.0.0.1", 0).then((server) {
+    HttpServer.bind("localhost", 0).then((server) {
       server.listen((request) {
         request.listen(
             (_) {},
             onDone: () {
               request.response.headers.contentType =
                   ContentType.parse(mimeType);
               request.response.add(content);
               request.response.close();
             });
       });
 
       var client = new HttpClient();
-      client.get("127.0.0.1", server.port, "/")
+      client.get("localhost", server.port, "/")
           .then((request) => request.close())
           .then(HttpBodyHandler.processResponse)
           .then((body) {
             expect(shouldFail, isFalse);
             expect(body.type, equals(type));
             expect(body.response, isNotNull);
             switch (type) {
               case "text":
               case "json":
                 expect(body.body, equals(expectedBody));
@@ skipping 39 matching lines @@
        true);
 }
 
 void testHttpServerRequestBody() {
   void test(String mimeType,
             List<int> content,
             dynamic expectedBody,
             String type,
             {bool shouldFail: false,
              Encoding defaultEncoding: UTF8}) {
-    HttpServer.bind("127.0.0.1", 0).then((server) {
+    HttpServer.bind("localhost", 0).then((server) {
       server.transform(new HttpBodyHandler(defaultEncoding: defaultEncoding))
           .listen((body) {
             if (shouldFail) return;
             expect(shouldFail, isFalse);
             expect(body.type, equals(type));
             switch (type) {
               case "text":
                 expect(body.request.headers.contentType.mimeType,
                        equals("text/plain"));
                 expect(body.body, equals(expectedBody));
@@ skipping 35 matching lines @@
 
               default:
                 throw "bad body type";
             }
             body.request.response.close();
           }, onError: (error) {
             if (!shouldFail) throw error;
           });
 
       var client = new HttpClient();
-      client.post("127.0.0.1", server.port, "/")
+      client.post("localhost", server.port, "/")
           .then((request) {
             if (mimeType != null) {
               request.headers.contentType =
                   ContentType.parse(mimeType);
             }
             request.add(content);
             return request.close();
           })
           .then((response) {
             if (shouldFail) {
@@ skipping 175 matching lines @@
   test('application/x-www-form-urlencoded',
        'name=%C8%A4%C8%A4'.codeUnits,
        { 'name' : 'ȤȤ' },
        "form");
 }
 
 void main() {
   testHttpClientResponseBody();
   testHttpServerRequestBody();
 }