I wanted to look at the increase in ntp traffic now that I've joined the pool.ntp.org ranks. Unfortunately munin didn't have a watch-port-x-and-draw-something-plugin. So I wrote my own based upon the ip_ plugin.

The plugin monitors both v6, v4, tcp and udp and plots them together, as send and received. Just symlink the port number to the plugin:

ip_port_123 -> ip_port_

For it to work, you do need some iptables rules, so yes, this plugin only works in Linux. See the munin plugin for the documentation.

Obligatory screenshot: