Wireshark is the industry standard protocol analyzer, also called a packet sniffer. You really don't need a HOWTO to install Wireshark, just install MacPorts and X11, and then use MacPorts to install Wireshark. After installation, start X11 and type "sudo wireshark" in a terminal window and the very user-friendly Wireshark X11 GUI starts up. Protocol analysis itself is a complex subject, so you may want to do some research on the web or by obtaining books on the subject to interpret the packet information.