Remote control,but error port 8081

i want to control my krakensdr remotely,there are 4g module connected in Pi4 and i have connected port 8081 to a website address,but my andriod app can`t read any infomation form my website address.

but if i connected to krakensdr wifi,it works.
and if i connect to,there are error page.

so what should i do to use my andriod app in 4G net?

is remote port are 8081?or i should read some correct doc?

This is the default IP for the WiFi hotspot broadcast by the Pi.

If you are instead connecting to the KrakenAndroid WiFi hotspot broadcast from your phone, then you’ll need to go into your phone settings and find the IP address of the KrakenSDR from there.