Hi Lane,
NI-VISA will let you do Modbus communication over TCP/IP, and you can use
LabVIEW for this. (LabVIEW also ships with NI-VISA.). The link
here provides a Modbus library that you can use to get started. You can also use the LabVIEW DSC Module; see the link
here for some more information. Hope this helps.
Regards,
Ebele O.
National Instruments