Assume our windows 7 machine A has no public IP - it's connected to LAN and has IP like 192.168. This machine has access to Internet. How to initiate remote access from this server machine A to be able manipulate of desktop of A by client machine B the same way RDP allows or something like that? Machine B has public IP and is connected somewhere in Internet - not in the same LAN with A. So there is possibility to establish connection from A to B but not possible from B to A. A should be controlled by B. In other words I should be capable to begin session from A and later work remotely from B with A's desktop. Updated: I have admin control only on my machine A and B.
if your B machine have a public ip address or you have full control on the router where is B machine and you can map the port forwarding, you can install on the B machine an openvpn server , tun device configuration, and generate a couple of key and certificate (there are a lot of tutorial on internet about it) then on the A machine you install an openvpn client, the right key and certificate generated on the B machine. when you start the openvpn client , the A and B machine add another logical ethernet card, with a couple of ip address. now you can start rdp using the new ip address, the tunnel bypass every router please be carefull, in some work environments is not 'allowed to create vpn or tunnel to the external, inform your network administrator first