KRDC appear to be an alternative to VNC. There are several VNC programs, one
favorite is "tight VNC".

If you want to access a computer which is behind a router, you will need to
learn about "port forwarding." You also need to deal with changes in your IP
address. Neither of those are very difficult, but a tutorial is 20 pages or so.
I found one online the first time I wanted to set up VNC.