How do I find what device is using a particular port on my network?

[steve23094]

Hi,

My router logs are displaying an error message every minute:
unknown daemon.warn miniupnpd[986]: SendSSDPNotify(): truncated output (515>=512)

A bit of searching leads me to believe it's a bug in my router firmware. It seems to be related to UPNP, I thought that I would turn off UPNP on the offending device. How do I go about identifying which device on my network is using port 986? I have a Mac.

Thanks.