Add an http_multi_server package.

pkg/http_multi_server/lib/src/utils.dart

Index: pkg/http_multi_server/lib/src/utils.dart
diff --git a/pkg/http_multi_server/lib/src/utils.dart b/pkg/http_multi_server/lib/src/utils.dart
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index 0000000000000000000000000000000000000000..9e95aba5f9d82612e7bf2d3632c762dd156e8ced
--- /dev/null
+++ b/pkg/http_multi_server/lib/src/utils.dart
@@ -0,0 +1,62 @@
+// Copyright (c) 2014, 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.
+
+library http_multi_server.utils;
+
+import 'dart:async';
+import 'dart:io';
+
+/// Merges all streams in [streams] into a single stream that emits all of their
+/// values.
+///
+/// The returned stream will be closed only when every stream in [streams] is
+/// closed.
+Stream mergeStreams(Iterable<Stream> streams) {
+  var subscriptions = new Set();
+  var controller;
+  controller = new StreamController(onListen: () {
+    for (var stream in streams) {
+      var subscription;
+      subscription = stream.listen(controller.add,
+          onError: controller.addError,
+          onDone: () {
+        subscriptions.remove(subscription);
+        if (subscriptions.isEmpty) controller.close();
+      });
+      subscriptions.add(subscription);
+    }
+  }, onCancel: () {
+    for (var subscription in subscriptions) {
+      subscription.cancel();
+    }
+  }, onPause: () {
+    for (var subscription in subscriptions) {
+      subscription.pause();
+    }
+  }, onResume: () {
+    for (var subscription in subscriptions) {
+      subscription.resume();
+    }
+  }, sync: true);
+
+  return controller.stream;
+}
+
+/// A cache for [supportsIpV6].
+bool _supportsIpV6;
+
+/// Returns whether this computer supports binding to IPv6 addresses.
+Future<bool> get supportsIpV6 {
+  if (_supportsIpV6 != null) return new Future.value(_supportsIpV6);
+
+  return ServerSocket.bind(InternetAddress.LOOPBACK_IP_V6, 0).then((socket) {
+    _supportsIpV6 = true;
+    socket.close();
+    return true;
+  }).catchError((error) {
+    if (error is! SocketException) throw error;
+    _supportsIpV6 = false;
+    return false;
+  });
+}