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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:
Beside these examples Wireshark can be helpful in many other situations too.
The following are some of the many features Wireshark provides:
However, to really appreciate its power you have to start using it.
Figure 1.1, “Wireshark captures packets and lets you examine their contents.” shows Wireshark having captured some packets and waiting for you to examine them.
Wireshark can capture traffic from many different network media types - and despite its name - including wireless LAN as well. Which media types are supported, depends on many things like the operating system you are using. An overview of the supported media types can be found at http://wiki.wireshark.org/CaptureSetup/NetworkMedia.
Wireshark can open packets captured from a large number of other capture programs. For a list of input formats see Section 5.2.2, “Input File Formats”.
Wireshark can save packets captured in a large number of formats of other capture programs. For a list of output formats see Section 5.3.2, “Output File Formats”.
There are protocol decoders (or dissectors, as they are known in Wireshark) for a great many protocols: see Appendix C, Protocols and Protocol Fields.
Wireshark is an open source software project, and is released under the GNU General Public License (GPL). You can freely use Wireshark on any number of computers you like, without worrying about license keys or fees or such. In addition, all source code is freely available under the GPL. Because of that, it is very easy for people to add new protocols to Wireshark, either as plugins, or built into the source, and they often do!
Here are some things Wireshark does not provide: