wrote: I hope its better to read all data bytes in the serial Buffer at once and Process a String Operation to Find the header and Data payload.
As somebody who did that early in his career, I can tell you that that is NOT the way to do it. It led to nothing but slow processing and major memory issues. Use the VISA buffer and read only what you need for your message and then use a Producer-Consumer to pass that message on to another loop for actual processing. This becomes especially needed when you have constant data coming through the serial port.