You can set this up via SSH if his system is configured correctly to accept this type of connection and you are able to configure the system via a terminal. You could also use a remote desktop tool like Teamviewer if you prefer a graphical view of the system.
In order to configure SSH you/client would need to do something like:
sudo apt-get install openssh-server- Install sshsudo nano /etc/ssh/sshd_config- Specify the listening port within this filesudo service ssh restart- Restart SSH- Set up a router rule to send ssh connections on that port to the desired system (you get the internal system internal IP using
ifconfig)
Something like this will work fine for a simple SSH connection.
If you want specifics on setup you would need to tell us what type of server the client is after. I assume from tags it is a web server, but is there a preference on installation or will apache be enough for the desired outcome?