             throw new Error "cannot create a ReceiverSession with a null channel!!!"
 
         super sessionManager, token, appId
+        @ppTimerId = null
         @timeout = Config.RECEIVER_SESSION_TIMEOUT
         @tag = "ReceiverSession"
 

            interval: Config.RECEIVER_SESSION_PP_INTERVAL
        @_onHeartbeat "ping"
        @triggerTimer()
        setInterval ( =>
                @_onHeartbeat "ping"
            ), Config.RECEIVER_SESSION_PP_INTERVAL


            if app and (app.getAppId() is @appId)
                app.terminate()
        @_clearTimer()
        if @ppTimerId
            clearTimeout @ppTimerId
        @sessionManager.clearReceiverSession()
        @channel.close()

