[libfreeradius-client] Send request to non-standard ports

Hi, I'm trying to send radius auth request to the 11812 port. So i've placed 11812 as second parameter of the rc_auth function. On my server's log, I can see that the NAS-PORT is set, in the request, to 11812. But the request itself is sent to the standard 1812 port .. How can I change that ? I need to send some request to 1812 and some others to 11812 (two radius servers are running). I've looked at the example code but they are just using the port parameter of rc_auth, so I can't find a way to make it work. (I'll need to do the same with accounting too) Thanks