Hi Garry,
the ISW switches do not support Cisco's proprietary UDLD.
They do support CFM, which can be used to check forwarding of Ethernet frames, but this is not supported by the Cisco Catalyst 3850.
A simple standards-based solution would be to use LACP. If one side stops receiving LACP PDUs, e.g. because data is forwarded in one direction only, that link will no longer be used for forwarding data.
Thanks,
Erik