Using Kerberos authentication for Server/Client application

The best place to start is the sample simple client and simple server in the MIT code distribution found here: https://github.com/krb5/krb5/tree/master/src/appl/sample

This shows you how to use GSSAPI to do mutual auth

I am not sure if you already have seen this, but the MIT Kerberos V5 API documentation looks pretty exhaustive.