Add ability to send a ping interval on a WebSocket.

sdk/lib/io/websocket_impl.dart

Index: sdk/lib/io/websocket_impl.dart
diff --git a/sdk/lib/io/websocket_impl.dart b/sdk/lib/io/websocket_impl.dart
index 33aec3f51f2fa1e8bd2c56a34e62d6f3b35c6016..c054b1ec9e0bc301a1004a05f04052951e6be5a3 100644
--- a/sdk/lib/io/websocket_impl.dart
+++ b/sdk/lib/io/websocket_impl.dart
@@ -455,7 +455,7 @@ class _WebSocketOutgoingTransformer extends StreamEventTransformer {
       return;
     }
     if (message is _WebSocketPing) {
-      addFrame(_WebSocketOpcode.PONG, message.payload, sink);
+      addFrame(_WebSocketOpcode.PING, message.payload, sink);
       return;
     }
     List<int> data;
@@ -571,6 +571,7 @@ class _WebSocketConsumer implements StreamConsumer {
   final Socket socket;
   StreamController _controller;
   StreamSubscription _subscription;
+  bool _issuedPause = false;
   Completer _closeCompleter = new Completer();
   Completer _completer;
 
@@ -582,11 +583,27 @@ class _WebSocketConsumer implements StreamConsumer {
     }
   }
 
+  void _onPause() {
+    if (_subscription != null) {
+      _subscription.pause();
+    } else {
+      _issuedPause = true;
+    }
+  }
+
+  void _onResume() {
+    if (_subscription != null) {
+      _subscription.resume();
+    } else {
+      _issuedPause = false;
+    }
+  }
+
   _ensureController() {
     if (_controller != null) return;
     _controller = new StreamController(sync: true,
-                                       onPause: () => _subscription.pause(),
-                                       onResume: () => _subscription.resume(),
+                                       onPause: _onPause,
+                                       onResume: _onResume,
                                        onCancel: _onListen);
     var stream = _controller.stream.transform(
         new _WebSocketOutgoingTransformer(webSocket));
@@ -627,6 +644,10 @@ class _WebSocketConsumer implements StreamConsumer {
           _done(error);
         },
         cancelOnError: true);
+    if (_issuedPause) {
+      _subscription.pause();
+      _issuedPause = false;
+    }
     return _completer.future;
   }
 
@@ -656,6 +677,9 @@ class _WebSocketImpl extends Stream implements WebSocket {
   bool _writeClosed = false;
   int _closeCode;
   String _closeReason;
+  Duration _pingInterval;
+  Timer _pingTimer;
+  _WebSocketConsumer _consumer;
 
   int _outCloseCode;
   String _outCloseReason;
@@ -734,17 +758,18 @@ class _WebSocketImpl extends Stream implements WebSocket {
 
   _WebSocketImpl._fromSocket(Socket this._socket,
                              [bool this._serverSide = false]) {
-    var consumer = new _WebSocketConsumer(this, _socket);
-    _sink = new _StreamSinkImpl(consumer);
+    _consumer = new _WebSocketConsumer(this, _socket);
+    _sink = new _StreamSinkImpl(_consumer);
     _readyState = WebSocket.OPEN;
 
     var transformer = new _WebSocketProtocolTransformer(_serverSide);
     _socket.transform(transformer).listen(
         (data) {
           if (data is _WebSocketPing) {
-            consumer.add(new _WebSocketPong(data.payload));
+            if (!_writeClosed) _consumer.add(new _WebSocketPong(data.payload));
           } else if (data is _WebSocketPong) {
-            // TODO(ajohnsen): Notify pong?
+            // Simply set pingInterval, as it'll cancel any timers.
+            pingInterval = _pingInterval;
           } else {
             _controller.add(data);
           }
@@ -785,6 +810,25 @@ class _WebSocketImpl extends Stream implements WebSocket {
                                      cancelOnError: cancelOnError);
   }
 
+  Duration get pingnterval => _pingInterval;
+
+  void set pingInterval(Duration interval) {
+    if (_writeClosed) return;
+    if (_pingTimer != null) _pingTimer.cancel();
+    _pingInterval = interval;
+
+    if (_pingInterval == null) return;
+
+    _pingTimer = new Timer(_pingInterval, () {
+      if (_writeClosed) return;
+      _consumer.add(new _WebSocketPing());
+      _pingTimer = new Timer(_pingInterval, () {
+        // No pong received.
+        close(WebSocketStatus.GOING_AWAY);
+      });
+    });
+  }
+
   int get readyState => _readyState;
 
   String get extensions => null;