Some additional comments:
Nagios plugin API is very simple - basically, plugin is an executable which return code indicates status of tested service (0 = OK, 1 = WARNING, 2 = CRITICAL, 3 = UNKNOWN), and one or more lines of text. So, you can run any nagios plugin from NetXMS agent as external parameter, and get either status code or first line of text output. For example, to get status code, add following line to nxagentd.conf:
ExternalParameter = NagiosTest1:nagios_plugin > /dev/null ; echo $?
and for capturing first line of plugin's text output simply
ExternalParameter = NagiosTest2:nagios_plugin
Best regards,
Victor