Wireshark (formerly Ethereal) 0.99.6a

Wireshark is a free network protocol analyzer for Windows and Unix The Ethereal network protocol analyzer has changed its name to Wireshark.
The name might be new, but the software is the same. Wiresharks powerful features make it the tool of choice for network troubleshooting, protocol development, and education worldwide.
Wireshark was written by networking experts around the world, and is an example of the power of open source
Wireshark is used by network professionals around the world for analysis, troubleshooting, software and protocol development and education.
The program has all of the standard features you would expect in a protocol analyzer, and several features not seen in any other product. Its open source license allows talented experts in the networking community to add enhancements.
Main features:
- Data can be captured "off the wire" from a live network connection, or read from a capture file.
- Wireshark can read capture files from tcpdump (libpcap), NAIs Sniffer (compressed and uncompressed), Sniffer Pro, NetXray, Sun snoop and atmsnoop, Shomiti/Finisar Surveyor, AIXs iptrace, Microsofts Network Monitor, Novells LANalyzer, RADCOMs WAN/LAN Analyzer, HP-UX nettl, i4btrace from the ISDN4BSD project, Cisco Secure IDS iplog, the pppd log (pppdump-format), the AG Groups/WildPackets EtherPeek/TokenPeek/AiroPeek, or Visual Networks Visual UpTime. It can also read traces made from Lucent/Ascend WAN routers and Toshiba ISDN routers, as well as the text output from VMSs TCPIPtrace utility and the DBS Etherwatch utility for VMS. Any of these files can be compressed with gzip and Ethereal will decompress them on the fly.
- Live data can be read from Ethernet, FDDI, PPP, Token-Ring, IEEE 802.11, Classical IP over ATM, and loopback interfaces (at least on some platforms; not all of those types are supported on all platforms).
- Captured network data can be browsed via a GUI, or via the TTY-mode "tethereal" program.
- Capture files can be programmatically edited or converted via command-line switches to the "editcap" program.
- 602 protocols can currently be dissected
- Output can be saved or printed as plain text or PostScript.
- Data display can be refined using a display filter.
- Display filters can also be used to selectively highlight and color packet summary information.
- All or part of each captured network trace can be saved to disk.