Closing Accounting Sessions at the end of Month

Hi all,I am using freeradius 3.0.12 with mysql.I want to close all open accounting sessions at the end of month to be able calculate monthly usages. Should i use radzap, or another better option? When i tried radzap as: radzap -N nas-ip radiusServer-ip secret i get: Sent Accounting-Request Id 4 from 0.0.0.0:39563 to radiusServer-ip:1813 length 38 #(3 trials)(0) No reply from server for ID 4 socket 3 What am i doing wrong? Thanks.