You could have downloaded WatchPort 1.2 for Mac from our software library for free. WatchPort for Mac lies within Internet & Network Tools, more precisely Network tools.
From the developer:
WatchPort allow you to listen to a specific port on your computer. When someone try to scan or connect to your port, his/her IP is logged.
You may want to check out more Mac applications, such as LaCie IPConfigurator or attach, which might be related to WatchPort.