clean stale sessions with radzap?

I use FR + mysql I try to clean some stale sessions from NAS's with dynamic ip's. I 'm logged in on the server and use radzap this way: radius1:~# radzap Usage: radzap [options] server[:port] secret So i try: radius1:~# radzap -u john localhost:1812 mysecret But this doesn't seem to be the right way? tnx yves