Hi.

I'd like to control my secondary PC (just for short periods and for learning reasons) via GUI over a LAN. I connect directly to it via an Ethernet cable.

I also want to permanently add the rule allowing this to UFW.
Something like this on PC#1 and vice versa on PC#2?
A program that comes to mind is Remmina. What packages must be installed on both computers? Would xvnc4viewer be needed?

PC#1 = Linux Mint 17 MATE
PC#2 = SolydX

I only use WiFi to connect to the Internet. I only connect the 2 computers via the Ethernet cable when I'm offline.

Cheers.

Remmina is a client that can connect via RDP, VNC, NX, XDMCP and SSH protocols. So you would need the desired appropriate server installed on the other computer. nx would be my first choice for remote desktops.

If you really want to learn then go strictly with a console ssh connection...