TCP/IP ports

> I'm trying to track down network traffic on our
> LAN. I'm seeing very frequent use of upper-level
> ports I don't recognize, like 4081. Does anyone
> know where you can go to get a comprehensive list
> of what ports are used by what
> systems/applications? Thanks for any help...
>
> Scott

>From this list: http://www.iana.org/assignments/port-numbers

#        4043-4095  Unassigned