linux - Finding current dynamic IP of a remote computer

I need to access a remote computer using VNC.
the computer has a static IP in its network but connects to Internet trough a VPN connection.
How can I find current IP of this computer from my own system (remotely)?
Can something like DynamicDNS help (e.g. ddclient && dnsomatic.com)? If Yes; does a free service exists?

Both systems run Linux

Thanks

Answer

Yes, some sort of dynamic DNS setup would work best. There are plenty of free dynamic DNS services, or you can run your own with a bit of BIND and nsclient.