Connecting LG GT540 (CyanogenMod 7.2.0, Android 2.3.7) & HTC One M7 via VNC for Remote Control

Hi! I would like to connect two smartphones with a network so that I can remotely control one of them. In this case, the controlled smartphone would be a rooted LG GT540 on CyanogenMod 7.2.0, version android 2.3.7. The controlling smartphone is to be HTC One m7 on the original system and without root.
I have installed the VNC server droid on LG and VNC Viewer on HTC. And it works, the HTC screen displays the LG screen and I can control it freely, but only when I have both smartphones connected to the same wifi network. If I turn off wifi on HTC and turn on cellular transfer, phones disconnect and cannot be connected this way. What am I doing wrong?

Through wifi, devices get on one subnet. This is no longer the case with cellular data.

But what do I have to do to be able to remotely control the device when it is on another network? I would like to leave one phone at home and go out with the other, having access to the phone that is left at home.

Use a VPN (virtual network) or use another program that allows you to connect via the cellular network (proxy server).

Alternatively, you can connect hamachi calls via VPN as your friend said.

Thanks a lot, guys. I used hamachi, and connected my phones with a VPN.
Problem solved, topic to be closed.