WinDump is the Windows version of tcpdump, the command line network analyzer for UNIX. WinDump is fully compatible with tcpdump and can be used to watch, diagnose and save to disk network traffic according to various complex rules. It can run under Windows 95, 98, ME, NT, 2000, XP, 2003 and Vista.
WinDump captures using the WinPcap library and drivers, which are freely downloadable from the WinPcap.org website. WinDump supports 802.11b/g wireless capture and troubleshooting through the Riverbed AirPcap adapter.
WinDump is free and is released under a BSD-style license.