generating ACCESS-CHALLENGE from radius server

Hi , I am planning to simulate ACCESS-CHALLENGE to authenticate the client which i plan to add it in pam-radius module (pam_radius-1.3.17) with out using radius server. Iam still reading the docs, incase if someone helps me with the following queries, it would be really helpful. I learned that the rlm_otp has the implementation of the same. Could anyone please let me know these: - any radius client which lets radius server to ask for ACCESS-CHALLENGE -- (echo 'User-Name="userX"'; echo 'CHAP-Password="secretpass"') | /usr/local/bin/radclient -x 192.168.11.94:1812 auth testing123 is not helping - how do i test rlm_otp module, any radius client program.. Regards, Pavan