The USB port is a type of serial port. It is, after all, the Universal SERIAL Bus. I wrote that twice because all of the books I have read on USB seem to muddle that quite a bit. There are some minor and major differences to how you use the USB ports but the idea is very much the same. I did this a while back and have to reread some stuff. (I also plan to either start a wiki book about USB or join one that is already started- I have to look into this more).