Welcome to the OptoForums! Sounds like an interesting application. You didn't mention which Opto 22 hardware/software pieces you have in the mix, but since this is on a PC I'm wondering if you're using/will use SoftPAC?
Or perhaps you're using one of our 232 modules like [SNAP-SCM-232? Or a 232 port on one of our [URL="http://www.opto22.com/site/pr_selector.aspx?cid=1&qs=1002#1043"]hardware-based controllers](http://www.opto22.com/site/pr_details.aspx?cid=1&item=SNAP-SCM-232)?
SoftPAC currently supports Ethernet only, but many of our customers use Ethernet-to-232 adapters (and most modern PCs don't have a 232 port on them anymore so that might be a good option to consider even if you DO happen to have a 232 port on your PC now).
Assuming you have a PAC in the mix somewhere, you'd want to use a Communication Handle in your PAC Control strategy. See the "Communication Commands" section of Chapter 10 "Programming with Commands" in form 1700, the PAC Control Users Guide for more info.
Any additional details you can provide on which Opto 22 hardware/software would help.
Also remember our support, pre-sales support, and training here in Temecula, CA are all FREE.
Hope that helps.