Excerpt from Wireshark User's Guide (3.7 mb) More documentation at http://www.wireshark.org/docs/ Wireshark is a network packet analyzer. A network packet analyzer will try to capture network packets and tries to display that packet data as detailed as possible. You could think of a network packet analyzer as a measuring device used to examine what's going on inside a network cable, just like a voltmeter is used by an electrician to examine what's going on inside an electric cable (but at a higher level, of course). In the past, such tools were either very expensive, proprietary, or both. However, with the advent of Wireshark, all that has changed. Wireshark is perhaps one of the best open source packet analyzers available today. Here are some examples people use Wireshark for: - network administrators use it to troubleshoot network problems - network security engineers use it to examine security problems - developers use it to debug protocol implementations - people use it to learn network protocol internals Beside these examples, Wireshark can be helpful in many other situations too. Download Wireshark (18 mb, Windows Installer 32-bit) Other versions at: http://www.wireshark.org/download.html