How to talk to a server that is not unity?

I have an authoritative game server that was not written in unity. Can I still use Unity’s NetworkManager to talk to my server so do I need to write my own sockets. I have been looking at the Unity documentation on the Networking classes and I feel like the client and server code gets mixed together and I have having a hard time seeing how they are used. Does anyone have an example (be it really rough) that might hint how I can talk to my server?
So just to be as clear as possible. I am only looking for help with the client part of this. The server is written in a different language and framework.
Thanks for the help

you can use Socket of C# to connect server

This may be of use… http://docs.unity3d.com/Manual/UNetMessages.html