[ZMQ] append a message sequence number to every ZMQ notification

src/zmq/zmqpublishnotifier.h

@@ -11,7 +11,19 @@ class CBlockIndex;
 
 class CZMQAbstractPublishNotifier : public CZMQAbstractNotifier
 {
+private:
+    uint32_t nSequence; //! upcounting per message sequence number
+
 public:
+
+    /* send zmq multipart message
+       parts:
+          * command
+          * data
+          * message sequence number
+    */
+    bool SendMessage(const char *command, const void* data, size_t size);
+
     bool Initialize(void *pcontext);
     void Shutdown();
 };