diff --git a/bin/rdfdb b/bin/rdfdb
--- a/bin/rdfdb
+++ b/bin/rdfdb
@@ -417,6 +417,9 @@ class WebsocketClient(cyclone.websocket.
             Failure(WebsocketDisconnect(reason)), self.wsClient)
 
     def messageReceived(self, message):
+        if message == 'PING':
+            self.sendMessage('PONG')
+            return
         log.info("got message from %r: %s", self.wsClient, message)
         p = Patch(jsonRepr=message)
         p.senderUpdateUri = self.wsClient.updateUri
diff --git a/light9/web/graph.coffee b/light9/web/graph.coffee
--- a/light9/web/graph.coffee
+++ b/light9/web/graph.coffee
@@ -77,6 +77,8 @@ class window.SyncedGraph
 
     @ws.onopen = =>
       log('connected to', fullUrl)
+      @resetStore()
+      @pingLoop()
 
     @ws.onerror = (e) =>
       log('ws error ' + e)
@@ -85,8 +87,17 @@ class window.SyncedGraph
       log('ws close')
 
     @ws.onmessage = (evt) =>
+      if evt.data == 'PONG'
+        return
       @onMessage(JSON.parse(evt.data))
 
+  pingLoop: () ->
+    if @ws.readyState == @ws.OPEN
+      @ws.send('PING')
+      
+      clearTimeout(@_pingLoopTimeout) if @_pingLoopTimeout?
+      @_pingLoopTimeout = setTimeout(@pingLoop.bind(@), 10000)
+
   onMessage: (msg) ->
     log('from rdfdb: ', msg)