fixed problem: protocol message was treated as audio packet

src/channel.cpp

@@ -583,11 +583,32 @@ EPutDataStat CChannel::PutData ( const CVector<unsigned char>& vecbyData,
 {
     EPutDataStat eRet = PS_GEN_ERROR;
 
+    // init flags
+    bool bIsProtocolPacket = false;
+    bool bIsAudioPacket    = false;
+    bool bNewConnection    = false;
+
     if ( bIsEnabled )
     {
-        bool bNewConnection = false;
-        bool bIsAudioPacket = false;
+        // first check if this is protocol data
+        // only use protocol data if channel is connected
+        if ( IsConnected() )
+        {
+            // this seems not to be an audio block, parse the message
+            if ( Protocol.ParseMessage ( vecbyData, iNumBytes ) )
+            {
+                // set status flags
+                eRet              = PS_PROT_OK;
+                bIsProtocolPacket = true;
 
+                // create message for protocol status
+                emit ProtocolStatus ( true );
+            }
+        }
+
+        // only try to parse audio if it was not a protocol packet
+        if ( !bIsProtocolPacket )
+        {
             // check if this is an audio packet by checking all possible lengths
             for ( int i = 0; i < MAX_NET_BLOCK_SIZE_FACTOR; i++ )
             {
@@ -647,26 +668,14 @@ for ( int i = 0; i < iCurNetwInBlSiFact * MIN_BLOCK_SIZE_SAMPLES; i++ ) {
             }
             else
             {
-            // only use protocol data if channel is connected
-            if ( IsConnected() )
-            {
-                // this seems not to be an audio block, parse the message
-                if ( Protocol.ParseMessage ( vecbyData, iNumBytes ) )
-                {
-                    eRet = PS_PROT_OK;
-
-                    // create message for protocol status
-                    emit ProtocolStatus ( true );
-                }
-                else
-                {
+                // the protocol parsing failed and this was no audio block,
+                // we treat this as protocol error (unkown packet)
                 eRet = PS_PROT_ERR;
 
                 // create message for protocol status
                 emit ProtocolStatus ( false );
             }
         }
-        }
 
         // inform other objects that new connection was established
         if ( bNewConnection )

src/protocol.cpp

@@ -15,10 +15,11 @@ Protocol message definition
 MAIN FRAME
 ----------
 
-    +------------+------------+------------------+--------------+-------------+
-    | 2 bytes ID | 1 byte cnt | 2 bytes length n | n bytes data | 2 bytes CRC |
-    +------------+------------+------------------+--------------+-------------+
+    +-------------+------------+------------+------------------+--------------+-------------+
+    | 2 bytes TAG | 2 bytes ID | 1 byte cnt | 2 bytes length n | n bytes data | 2 bytes CRC |
+    +-------------+------------+------------+------------------+--------------+-------------+
 
+- TAG is an all zero bit word to identify protocol messages
 - message ID defined by the defines PROTMESSID_x
 - cnt: counter which is increment for each message and wraps around at 255
 - length n in bytes of the data
@@ -639,6 +640,15 @@ bool CProtocol::ParseMessageFrame ( const CVector<uint8_t>& vecIn,
     // decode header -----
     iCurPos = 0; // start from beginning
 
+    // 2 bytes TAG
+    const int iTag = static_cast<int> ( GetValFromStream ( vecIn, iCurPos, 2 ) );
+
+    // check if tag is correct
+    if ( iTag != 0 )
+    {
+        return false; // return error code
+    }
+
     /* 2 bytes ID */
     iID = static_cast<int> ( GetValFromStream ( vecIn, iCurPos, 2 ) );
 
@@ -715,9 +725,8 @@ void CProtocol::GenMessageFrame ( CVector<uint8_t>& vecOut,
     // query length of data vector
     const int iDataLenByte = vecData.Size();
 
-    // total length of message = 7 + "iDataLenByte"
-    // 2 byte ID + 1 byte cnt + 2 byte length + n bytes data + 2 bytes CRC
-    const int iTotLenByte = 7 + iDataLenByte;
+    // total length of message
+    const int iTotLenByte = MESS_LEN_WITHOUT_DATA_BYTE + iDataLenByte;
 
     // init message vector
     vecOut.Init( iTotLenByte );
@@ -725,15 +734,19 @@ void CProtocol::GenMessageFrame ( CVector<uint8_t>& vecOut,
     // encode header -----
     unsigned int iCurPos = 0; // init position pointer
 
-    /* 2 bytes ID */
+    // 2 bytes TAG (all zero bits)
+    PutValOnStream ( vecOut, iCurPos,
+        static_cast<uint32_t> ( 0 ), 2 );
+
+    // 2 bytes ID
     PutValOnStream ( vecOut, iCurPos,
         static_cast<uint32_t> ( iID ), 2 );
 
-    /* 1 byte cnt */
+    // 1 byte cnt
     PutValOnStream ( vecOut, iCurPos,
         static_cast<uint32_t> ( iCnt ), 1 );
 
-    /* 2 bytes length */
+    // 2 bytes length
     PutValOnStream ( vecOut, iCurPos,
         static_cast<uint32_t> ( iDataLenByte ), 2 );
 

src/protocol.h

@@ -48,8 +48,8 @@
 #define PROTMESSID_CHANNEL_NAME             18 // set channel name for fader tag
 
 // lengths of message as defined in protocol.cpp file
-#define MESS_HEADER_LENGTH_BYTE         5 /* ID, cnt, length */
-#define MESS_LEN_WITHOUT_DATA_BYTE      ( MESS_HEADER_LENGTH_BYTE + 2 /* CRC */ )
+#define MESS_HEADER_LENGTH_BYTE         7 /* TAG (2), ID (2), cnt (1), length (2) */
+#define MESS_LEN_WITHOUT_DATA_BYTE      ( MESS_HEADER_LENGTH_BYTE + 2 /* CRC (2) */ )
 
 // time out for message re-send if no acknowledgement was received
 #define SEND_MESS_TIMEOUT_MS            400 // ms