[SIL-279] Fix offset calculation for SNAP7 I/O

silecs-communication-cpp/src/silecs-communication/interface/communication/SNAP7Connection.cpp

@@ -243,6 +243,7 @@ int SNAP7Connection::readIO(PLC* thePLC, unsigned long address, unsigned long of
     //DATA topic makes sense with RECV one
     if (RECV & Log::topics_) LOG(DATA) << "Read data, address: " << address << ", ofs: " << offset << ", byte-size: " << size;
 
+    address += offset;
     err = Cli_EBRead(recvClient_, (int)address, (int)size, (void *)pBuffer);
     checkError(thePLC, err, false); // close the connection, will try again at the next access
   }
@@ -260,6 +261,7 @@ int SNAP7Connection::writeIO(PLC* thePLC, unsigned long address, unsigned long o
             //DATA topic makes sense with SEND one
             if (SEND & Log::topics_) LOG(DATA) << "Write data, address: " << address << ", ofs: " << offset << ", byte-size: " << size;
 
+            address += offset;
             err = Cli_ABWrite(sendClient_, (int)address, (int)size, (void *)pBuffer);
             checkError(thePLC, err, false); // close the connection, will try again at the next access
       }
@@ -271,7 +273,7 @@ bool SNAP7Connection::checkError(PLC* thePLC, int err, bool retry)
 {
     if (err != 0)
     {
-        LOG(COMM) << "Transaction failure with PLC: " << thePLC->getName() << getErrorMessage(err);
+        LOG(COMM) << "Transaction failure with PLC: " << thePLC->getName() << " " << getErrorMessage(err);
 
         if (retry)
         {