This library provides services for creating and sending RADIUS requests and receiving and decoding RADIUS replies. It also provides a class for managing a UDP Socket, over which RADIUS requests are sent and received.
It is designed to be used with the Arduino Ethernet shield and ArduinoMega. The size of the binary is such that a complete RADIUS client is too big for an Arduino Diecimila (which the Ethernet shield is designed for), and you need an ArduinoMega or similar. Unfortunately, you need to make some special hardware arrangements to make the Ethernet shield work with Arduino Mega, although no soldering is required: see http://mcukits.com/2009/04/06/arduino-ethernet-shield-mega-hack/ and http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1252386632 Note that 3 pins on the Ethernet shield must be bent out of the way to make this work.
The latest version of this documentation can be downloaded from http://www.airspayce.com/mikem/arduino/Radius
The version of the package that this documentation refers to can be downloaded from http://www.airspayce.com/mikem/arduino/Radius/Radius-1.2.zip
The package includes a sample RadiusClient sketch, which gives a working example of how to use the library.