Sniffer v1.0 for Mac OS X

Sniffer is a free, general purpose network traffic monitor and packet
capture program for Mac OS X. It is capable of monitoring and logging all
network traffic on ethernet and ppp network interfaces. ICMP, UDP and TCP
message payloads can be viewed directly in the program’s hex-editor view.
Sniffer is a very useful network monitoring tool, and it’s free! Requires
Mac OS X.