Purpose : Some times Isp Or vps provider they block port 5666 Or for any reason if you want to configure nrpe to listen different port example 15666, follow as bellow: On the Remote host(linux-vps) : 1. Change the Port number in : /etc/xinetd.d/nrpe # default: on # description: NRPE (Nagios Remote Plugin Executor) service [...]