I/O registers in the Barionet (1000 instances) either are tied to hardware or just hold values, as an interface to a BCL program in the Barionet. Registers can be polled and also controlled using standard SNMP get/set requests. For set operations, the write community "privat" needs to be used . You can easily control the relays, for example, by using SNMP set requests on registers 1 and 2.
The detailed register map is documented in the Barionet manual.