Control an Onkyo receiver via IP using basic driver

Hi, has anyone tried to control an onkyo Receiver or similar using the basic driver?   The command protocol looks simple with one major exception - you need to calculate the length of the command and send this as part of the message in bigendian format.. is there any way to hack this together in bOS?  I guess if you limit yourself to commands of fixed length it will be possible?? ..  the protocol as I found it on the internet is attached if useful to anyone... Onkyo Serial AVR_5-17.xlsx