Dahua DMSS Remote Unlock Setup

I need my Dahua intercom pair (VTO door station and VTH indoor monitor) configured so that, when I am off-site, I can press a button in the Dahua DMSS app and release the door/gate lock. The call itself can keep ringing on the indoor screen; the priority here is reliable, real-time remote unlocking from my phone. That means: • Correctly binding the VTH to DMSS, enabling P2P or another secure method so the unlock relay reacts instantly. • Verifying permissions in DMSS so only authorised phones trigger the command. • Testing the full flow: press unlock inside DMSS → VTH receives → door/gate relay clicks open. Please walk me through any port-forwarding, firmware, or network tweaks you apply so I can reproduce the setup later if needed. A short step-by-step document or recorded screen share of the final settings will complete the job.