From OpenNMS

Ports used by OpenNMS

OpenNMS Server

The following Ports are used on the OpenNMS Server.

Note: those are the default values which may be changed in the appropriate config files.

httpAdaptor     8180
rtc             5817
jetty           8980
jetty / https   8443
jetty / ajp     8981

syslogd         514 or 1514
snmp trap       162
(vulnscan        1241)

Ports scanned by OpenNMS

There is a large number of ports which can be scannd by OpenNMS. Look in capsd and poller configuration for explanations.