Berkeley Packet Monitor can be used to monitor network traffic.
Berkeley Packet Monitor is an application that can be used to monitor network traffic. This program uses the “Berkeley Packet Filter” (/dev/bpf) devices built into the Mac OS X operating system to log and re-assemble all packets entering and exiting from a specified network interface.
Berkeley Packet Monitor can be configured to log ICMP, TCP, and UDP packets, and will allow users to view the raw data contained within each packet sent or received.