I had a more complex challenge in that I am at home (or somewhere else) and my setup is at a remote location without WiFi access, only 4G. Still, this could be solved.
I am assuming your ASIAir is connected to your home WiFi? So a simplified version of my solution (see chart below) should work.
As was mentioned before, VPN by Tailscale is probably the easiest way to go. The biggest question here is if your router has native Tailscale support. I bought a small travel router for my onsite area which does, so setup is very simple in my case - but it should generally work on all standard routers.
The router and iPhone need to be added to the Tailscale network - if it is configured properly, you can then open the ASIAir app on your iPhone and connect to the ASIAir by inputting its internal IP.
