gss-token is simple program that generates and consumes BASE64 encoded GSS tokens. It comes in handy when testing as you can cut and paste the tokens between terminal windows to test the Kerberos rather than having to have a client/server (like knc(1)) program to do it. It’s especially helpful when you have firewalls to configure to let extra ports through.
HTTP SPNEGO authentication also uses base64 tokens and gss-token supports add that text on with the -N flag:
$ curl -H "Authorization: $(gss-token -N HTTP@server)" \ > https://server/path/to/file
will opportunistically send a GSSAPI authentication with your HTTP request.