Add Server.isClosed and Client.isClosed.

lib/src/server.dart

 // 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 json_rpc_2.server;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 
@@ skipping 25 matching lines @@
   ///
   /// These are tried in order until one of them doesn't throw a
   /// [RpcException.methodNotFound] exception.
   final _fallbacks = new Queue<Function>();
 
   /// Returns a [Future] that completes when the connection is closed.
   ///
   /// This is the same future that's returned by [listen].
   Future get done => _streams.done;
 
+  /// Whether the connection is closed.
+  bool get isClosed => _streams.isClosed;
+
   /// Creates a [Server] that reads requests from [requests] and writes
   /// responses to [responses].
   ///
   /// If [requests] is a [StreamSink] as well as a [Stream] (for example, a
   /// `WebSocket`), [responses] may be omitted.
   ///
   /// Note that the server won't begin listening to [requests] until
   /// [Server.listen] is called.
   Server(Stream<String> requests, [StreamSink<String> responses]) {
     _streams = new TwoWayStream("Server", requests, "requests",
@@ skipping 78 matching lines @@
       if (request.isEmpty) {
         return new RpcException(error_code.INVALID_REQUEST, 'A batch must '
             'contain at least one request.').serialize(request);
       }
 
       return Future.wait(request.map(_handleSingleRequest)).then((results) {
         var nonNull = results.where((result) => result != null);
         return nonNull.isEmpty ? null : nonNull.toList();
       });
     }).then((response) {
-      if (response != null) _streams.add(response);
+      if (!_streams.isClosed && response != null) _streams.add(response);
     });
   }
 
   /// Handles an individual parsed request.
   Future _handleSingleRequest(request) {
     return syncFuture(() {
       _validateRequest(request);
 
       var name = request['method'];
       var method = _methods[name];
@@ skipping 89 matching lines @@
       return syncFuture(() => iterator.current(params)).catchError((error) {
         if (error is! RpcException) throw error;
         if (error.code != error_code.METHOD_NOT_FOUND) throw error;
         return _tryNext();
       });
     }
 
     return _tryNext();
   }
 }