Looks like you're missing the open command after the SetCommunicationHandleValue and before the TransmitString, something like this:
open_status = OpenOutgoingCommunication( Test_Handle );
Don't forget to check the return codes, like your status after your TransmitString executed was probably -52 meaning "not open yet." The return values are usually pretty handy when troubleshooting comm handle code.
I'm making some assumptions here, like didn't have that open somewhere else, but I can't explain how the empty file got there unless it was leftover from something else? In any case, if you're still having trouble, let us know your firmware version, etc. and we'll get it sorted out for you.