implementing heartbeat

src/WebSocketsClient.h

@@ -86,6 +86,9 @@ class WebSocketsClient: private WebSockets {
 
         void setReconnectInterval(unsigned long time);
 
+        void enableHeartbeat(uint32_t pingInterval, uint32_t pongTimeout, uint8_t disconnectTimeoutCount);
+        void disableHeartbeat();        
+
     protected:
         String _host;
         uint16_t _port;
@@ -115,6 +118,8 @@ class WebSocketsClient: private WebSockets {
         void connectedCb();
         void connectFailedCb();
 
+        void handleHBPing(); // send ping in specified intervals
+
 #if (WEBSOCKETS_NETWORK_TYPE == NETWORK_ESP8266_ASYNC)
         void asyncConnect();
 #endif