I'm running one of these GW-21 units . Just set it up, spent a little time getting the comm right and it seems like the ticket. I can run long lines , ethernet, to the unit and the old rs-232 from the unit to the VF-0.
It's here
http://www.neteon.net/
The trick is that it creates a virtual comm port...so when you hit 'send', it thinks it a normal, default com port, and fires it out your ethernet line instead of the rs-232.
$109. plus shipping.....