>>I sort of have this working now. Two problems...
>>
>>1. When I change the senders RTS line, the receiver (VB activex DLL) oncomm fires three times.
>>
>
>Sure - you're causing multiple events since you're 'pinging' the handshake line - OnComm sees two transits of the CTS line (RTS crosses CTS), which issues two comEvCTS, and probably a Send buffer not full (comEvSend) report.
>

I'm not sure why it would see two transitions. Just as a test I set it from high to low and with that I get three events. I have logged all
the events by capturing and appending the event number to a string. I get three 3s in a row. I have not sent any data in this test.

>>2. When the com activities are done I need to return about 2K in text. Can I send that back
>> from the dll?
>
>Yep - you can adjust the rThreshold and InBuffer size if you like, you need not respond to each discrete character received in order to avoid buffer overrun with the default 512 byte buffer and your data rate, unless it's a very slow and busy system.