preller: It's likely not as featureful as Wireshark, but it is a native Mac application, so X11 is not required.

how is this app compared to wireshark?

Cocoa Packet Analyzer worked for me out-of-the-box.

Of course I started my packet quest by installing Wireshark, but upon capture attempt, /dev/bpf0 could not be written. There is documentation for fixing this, and perhaps it is simple--I did not try.