don't futher process plain Ack

Streaming.cpp

@@ -54,6 +54,14 @@ namespace stream
 			m_SendStreamID = packet->GetReceiveStreamID (); 	
 
 		uint32_t receivedSeqn = packet->GetSeqn ();
+		if (!receivedSeqn && !packet->IsSYN ())
+		{
+			// plain ack
+			LogPrint ("Plain ACK received");
+			delete packet;
+			return;
+		}
+
 		LogPrint ("Received seqn=", receivedSeqn); 
 		if (!receivedSeqn || receivedSeqn == m_LastReceivedSequenceNumber + 1)
 		{			

Streaming.h

@@ -55,6 +55,8 @@ namespace stream
 		uint16_t GetOptionSize () const { return be16toh (*(uint16_t *)GetOption ()); };
 		const uint8_t * GetOptionData () const { return GetOption () + 2; };
 		const uint8_t * GetPayload () const { return GetOptionData () + GetOptionSize (); };
+
+		bool IsSYN () const { return GetFlags () & PACKET_FLAG_SYNCHRONIZE; };
 	};	
 
 	struct PacketCmp