No, I haven't found any way to make that work. It would require quite a rewrite and some code for handling multicast UDP, and there is no standard library for that for VB6 programs.

As far as I can tell a Windows Server that relays Mailslot broadcasts among your VLANs would solve this. Domain Controllers should do that but often people don't connect them directly to every VLAN.

You may have to look for another alternative.