What are the Basics of packet programming?

I am assign to program to send a packet header to a device through a serial port program...

I am not sure how to program a packet header like, do i convert the commands to binary or hexa...?How am i going to encapsulate the packets..?

Thanks

Here is an analogous question: There is guy in the corner of the bar, I wanna talk to him so should I speak in japanese or russian?

You need to know what the device you are talking to (i'm assuming there is actually a device and you aren't talking to a unused port) wants. If it needs a certain header than give it what it wants. That is where protocols like TWAIN and winspool come into play. As for the second part of the question (the part I patronized) the computer speaks in binary. It would be a lot of help if you tell me exactly what your game plan is here.

Ok for sending a packet to whatever source, how i keep the data inside the packet.
the header is something like this

<SOH> |<ETX> | <FF> | <NUL>

<SOH>= start of header
<ETX>= end of text
<FF>= form feed
<NUL>= null

Thanks

does this even belong in c++ programming?

Erm...
THis is the packet to send to the destination.
the layout of the packet. :)
I need to use c to send it.