Host cannot talk to remote host



I have finish install and configure nagios server. On monitor page I can see win2k server that i add last week. Now i want to debian remote host. My nagios server run using fedora 9. On debian box i can see port 5666 open.

On debian box, i already install nrpe_plugin. Is there other thing i need to install on debian or fedora/nagios box?

But nagios cannot talk to debian box. I don’t know what wrong. Still investigate. Anyone please assist me.