Eavesdrop is an application for listening in on TCP conversations on the network your computer is attached to. See Notes for Newbies if you have not worked with a network sniffer before. Since this application only processes TCP, it may not capture all traffic on the machine you run it on. If you need more network analysis, I strongly suggest you look into other applications, such as tcpdump (available in Mac OS X 10.3+ already) and Wireshark (available through fink or darwin ports).
I have started a new version of Eavesdrop that will be a complete re-write from the ground up. I will be posting more details as I work on things, but I make no promises in how long things might take. See the New Version section for more information.
Some requests for help. If you know anything about GNUStep for Linux or how ethereal is coded, I would love to talk to you. I would like to be able to implement remote capturing using both Mac OS X and Linux boxes as the capture server. Also, I would like to be able to support dissectors in a similar fashion to ethereal, if possible, so I can leverage off of what that community has done.
Eavesdrop source is now available on-line through Google Code. You can check out the subversion repository for either the currently released version or the new version in development. You can go to the project site or directly to the source code.