Change hasSubscribers to hasListener.

sdk/lib/io/secure_server_socket.dart

 // Copyright (c) 2012, 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.
 
 part of dart.io;
 
 /**
  * The [SecureServerSocket] is a server socket, providing a stream of high-level
  * [Socket]s.
  *
@@ skipping 204 matching lines @@
 
   void _onPauseStateChange() {
     if (_controller.isPaused) {
       _subscription.pause();
     } else {
       _subscription.resume();
     }
   }
 
   void _onSubscriptionStateChange() {
-    if (_controller.hasSubscribers) {
+    if (_controller.hasListener) {
       _subscription = _socket.listen(_onData,
                                      onDone: _onDone,
                                      onError: _onError);
     } else {
       close();
     }
   }
 }