The FreeRADIUS Client is a framework and library for writing RADIUS
Clients which additionally includes radlogin, a flexible RADIUS aware
login replacement, a command line program to send RADIUS
authentication/authorisation requests and accounting records and a
utility to query the status of a RADIUS server.  All these programs are
based on a library which lets you develop a RADIUS-aware application in
less than 50 lines of C code. It is highly portable and runs on Linux,
many BSD variants and Solaris.

WWW: http://wiki.freeradius.org/Radiusclient