Bind to all available loopback addresses in pub.

sdk/lib/_internal/pub/lib/src/io.dart

Index: sdk/lib/_internal/pub/lib/src/io.dart
diff --git a/sdk/lib/_internal/pub/lib/src/io.dart b/sdk/lib/_internal/pub/lib/src/io.dart
index 6e119735a0b55f2e6b48199d49f36c0d8e88cce5..5ae64c2489f7144a13fd7770deca42c64ab16c70 100644
--- a/sdk/lib/_internal/pub/lib/src/io.dart
+++ b/sdk/lib/_internal/pub/lib/src/io.dart
@@ -12,6 +12,7 @@ import 'dart:io';
 
 import 'package:path/path.dart' as path;
 import 'package:http/http.dart' show ByteStream;
+import 'package:http_multi_server/http_multi_server.dart';
 import 'package:stack_trace/stack_trace.dart';
 
 import 'exit_codes.dart' as exit_codes;
@@ -686,6 +687,15 @@ Future withTempDir(Future fn(String path)) {
   });
 }
 
+/// Binds an [HttpServer] to [host] and [port].
+///
+/// If [host] is "localhost", this will automatically listen on both the IPv4
+/// and IPv6 loopback addresses.
+Future<HttpServer> bindServer(String host, int port) {
+  if (host == 'localhost') return HttpMultiServer.loopback(port);
+  return HttpServer.bind(host, port);
+}
+
 /// Extracts a `.tar.gz` file from [stream] to [destination]. Returns whether
 /// or not the extraction was successful.
 Future<bool> extractTarGz(Stream<List<int>> stream, String destination) {