Measuring vehicle speed using odb2

I'm trying to get a speed reading from odb2.
I built a small program but it returns unclear values ​​probably in ASCII

Who can help what are the correct commands I need to send and how to translate the result I get per km / h

I also have an idea to connect another phone as an intermediary between my phone and ODB2 and thus discover all the data traffic.
Is it practical?

Unless you like living inside an ASCII table,
use the BlueTooth ReceiveText block instead of the Receive Unsigned Bytes block.