How to make all connections to a sever happen over OpenVPN?

Hello,

I have a server setup with OpenVPN installed + an ASA, I'm able to make connections with configured clients. Now I want every connection that happens like SSH, VNC, etc, to work if and only if the client has the VPN connection and refuse everything/everyone else. Can I do this with one server only or do I need another server for that? How would something like that work or be setup? Any help would be appreciated.