Yes, it’s go through ethernet directly to VT and use same protocol as for events (you can open lock using http protocol as well as it’s done at Dahua VTO to MQTT Broker) but I think to use same communication for opening the lock it’s more reliable than http. Integration open the lock exactly as Dahua DMSS application.
What you mean under terminals - Dahua VTH devices?
BTW You can use same integration for Dahua VTH devices but you should look to events which you will receive and thinks if it’s report something useful for you.