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[[ChapterIntroduction]]

== Introduction

[[ChIntroWhatIs]]

=== What is Wireshark?

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.

[[ChIntroPurposes]]

==== Some intended purposes

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.

[[ChIntroFeatures]]

==== Features

The following are some of the many features Wireshark provides:

* Available for _UNIX_ and _Windows_.

* _Capture_ live packet data from a network interface.

* _Open_ files containing packet data captured with tcpdump/WinDump, Wireshark, and a number of other packet capture programs.

* _Import_ packets from text files containing hex dumps of packet data.

* Display packets with _very detailed protocol information_.

* _Save_ packet data captured.

* _Export_ some or all packets in a number of capture file formats.

* _Filter packets_ on many criteria.

* _Search_ for packets on many criteria.

* _Colorize_ packet display based on filters.

* Create various _statistics_.

*  ...and _a lot more!_

However, to really appreciate its power you have to start using it.

<<ChIntroFig1>> shows Wireshark having captured some packets and waiting for you
to examine them.

[[ChIntroFig1]]
.Wireshark captures packets and lets you examine their contents.
image::wsug_graphics/ws-main.png[{screenshot-attrs}]

==== Live capture from many different network media

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
link:{wireshark-wiki-url}CaptureSetup/NetworkMedia[].

==== Import files from many other capture programs

Wireshark can open packets captured from a large number of other capture
programs. For a list of input formats see <<ChIOInputFormatsSection>>.

==== Export files for many other capture programs

Wireshark can save packets captured in a large number of formats of other
capture programs. For a list of output formats see <<ChIOOutputFormatsSection>>.

==== Many protocol dissectors

There are protocol dissectors (or decoders, as they are known in other products)
for a great many protocols: see <<AppProtocols>>.

==== Open Source Software

Wireshark is an open source software project, and is released under the
{gplv2-url}[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!

[[ChIntroNoFeatures]]

==== What Wireshark is not

Here are some things Wireshark does not provide:

* Wireshark isn't an intrusion detection system. It will not warn you when
  someone does strange things on your network that he/she isn't allowed to do.
  However, if strange things happen, Wireshark might help you figure out what is
  really going on.

* Wireshark will not manipulate things on the network, it will only "measure"
  things from it. Wireshark doesn't send packets on the network or do other
  active things (except for name resolutions, but even that can be disabled).

[[ChIntroPlatforms]]

=== System Requirements

The amount of resources Wireshark needs depends on your environment and on the
size of the capture file you are analyzing. The values below should be fine for
small to medium-sized capture files no more than a few hundred MB. Larger
capture files will require more memory and disk space.

[NOTE]
.Busy networks mean large captures
====
Working with a busy network can easily produce huge capture files. Capturing on
a gigabit or even 100 megabit network can produce hundreds of megabytes of
capture data in a short time. A fast processor, lots of memory and disk
space is always a good idea.
====

If Wireshark runs out of memory it will crash. See
{wireshark-wiki-url}KnownBugs/OutOfMemory for details and workarounds.

Although Wireshark captures packets using a separate process the main interface
is single-threaded and won't benefit much from multi-core systems.

==== Microsoft Windows

* The current version of Wireshark should support any version of Windows that is
  still within its http://windows.microsoft.com/en-us/windows/lifecycle[extended
  support lifetime]. At the time of writing this includes Windows 10, 8, 7, Vista,
  Server 2016, Server 2012 R2, Server 2012, Server 2008 R2, and Server 2008.

* Any modern 64-bit AMD64/x86-64 or 32-bit x86 processor.

* 400 MB available RAM. Larger capture files require more RAM.

* 300 MB available disk space. Capture files require additional disk space.

* 1024&#xd7;768 (1280&#xd7;1024 or higher recommended) resolution with at
  least 16 bit color. 8 bit color should work but user experience will be
  degraded. Power users will find multiple monitors useful.

* A supported network card for capturing

  - Ethernet. Any card supported by Windows should work. See the wiki pages on
    link:{wireshark-wiki-url}CaptureSetup/Ethernet[Ethernet capture] and
    link:{wireshark-wiki-url}CaptureSetup/Offloading[offloading] for issues that
    may affect your environment.

  - 802.11. See the {wireshark-wiki-url}CaptureSetup/WLAN#Windows[Wireshark
    wiki page]. Capturing raw 802.11 information may be difficult without
    special equipment.

  - Other media. See link:{wireshark-wiki-url}CaptureSetup/NetworkMedia[].

Older versions of Windows which are outside Microsoft's extended lifecycle
support window are no longer supported. It is often difficult or impossible to
support these systems due to circumstances beyond our control, such as third
party libraries on which we depend or due to necessary features that are only
present in newer versions of Windows (such as hardened security or memory
management).

Wireshark 1.12 was the last release branch to support Windows Server
2003. Wireshark 1.10 was the last branch to officially support Windows
XP. See the link:{wireshark-wiki-url}Development/LifeCycle[Wireshark
release lifecycle] page for more details.

==== UNIX / Linux

Wireshark runs on most UNIX and UNIX-like platforms including macOS and
Linux. The system requirements should be comparable to the Windows
values listed above.

Binary packages are available for most Unices and Linux distributions
including the following platforms:

* Apple macOS

* Debian GNU/Linux

* FreeBSD

* Gentoo Linux

* HP-UX

* Mandriva Linux

* NetBSD

* OpenPKG

* Red Hat Enterprise/Fedora Linux

* Sun Solaris/i386

* Sun Solaris/SPARC

* Canonical Ubuntu

If a binary package is not available for your platform you can download
the source and try to build it. Please report your experiences to
mailto:{wireshark-dev-list-email}[].

[[ChIntroDownload]]

=== Where to get Wireshark

You can get the latest copy of the program from the Wireshark website at
{wireshark-download-url}. The download page should automatically
highlight the appropriate download for your platform and direct you to
the nearest mirror. Official Windows and macOS installers are signed by
the *Wireshark Foundation*.

A new Wireshark version typically becomes available each month or two.

If you want to be notified about new Wireshark releases you should subscribe to
the wireshark-announce mailing list. You will find more details in
<<ChIntroMailingLists>>.

[[ChIntroHistory]]


=== A brief history of Wireshark

In late 1997 Gerald Combs needed a tool for tracking down network problems
and wanted to learn more about networking so he started writing Ethereal (the
original name of the Wireshark project) as a way to solve both problems.

Ethereal was initially released after several pauses in development in July
1998 as version 0.2.0. Within days patches, bug reports, and words of
encouragement started arriving and Ethereal was on its way to success.

Not long after that Gilbert Ramirez saw its potential and contributed a
low-level dissector to it.

In October, 1998 Guy Harris was looking for something better than tcpview so he
started applying patches and contributing dissectors to Ethereal.

In late 1998 Richard Sharpe, who was giving TCP/IP courses, saw its potential
on such courses and started looking at it to see if it supported the protocols
he needed. While it didn't at that point new protocols could be easily added.
So he started contributing dissectors and contributing patches.

The list of people who have contributed to the project has become very long
since then, and almost all of them started with a protocol that they needed that
Wireshark or did not already handle. So they copied an existing dissector and
contributed the code back to the team.

In 2006 the project moved house and re-emerged under a new name: Wireshark.

In 2008, after ten years of development, Wireshark finally arrived at version
1.0. This release was the first deemed complete, with the minimum features
implemented. Its release coincided with the first Wireshark Developer and User
Conference, called Sharkfest.

In 2015 Wireshark 2.0 was released, which featured a new user interface.

[[ChIntroMaintenance]]

=== Development and maintenance of Wireshark

Wireshark was initially developed by Gerald Combs. Ongoing development and
maintenance of Wireshark is handled by the Wireshark team, a loose group of
individuals who fix bugs and provide new functionality.

There have also been a large number of people who have contributed
protocol dissectors to Wireshark, and it is expected that this will
continue. You can find a list of the people who have contributed code to
Wireshark by checking the about dialog box of Wireshark, or at the
link:{wireshark-authors-url}[authors] page on the Wireshark web site.

Wireshark is an open source software project, and is released under the
{gplv2-url}[GNU General Public License] (GPL) version 2. All source code is
freely available under the GPL. You are welcome to modify Wireshark to suit your
own needs, and it would be appreciated if you contribute your improvements back
to the Wireshark team.

You gain three benefits by contributing your improvements back to the community:

. Other people who find your contributions useful will appreciate them, and you
  will know that you have helped people in the same way that the developers of
  Wireshark have helped people.

. The developers of Wireshark might improve your changes even more, as there's
  always room for improvement. Or they may implement some advanced things on top
  of your code, which can be useful for yourself too.

. The maintainers and developers of Wireshark will maintain your code as well,
  fixing it when API changes or other changes are made, and generally keeping it
  in tune with what is happening with Wireshark. So if Wireshark is updated
  (which is done often), you can get a new Wireshark version from the website
  and your changes will already be included without any effort for you.

The Wireshark source code and binary kits for some platforms are all
available on the download page of the Wireshark website:
{wireshark-download-url}.

[[ChIntroHelp]]

=== Reporting problems and getting help

If you have problems or need help with Wireshark there are several places that
may be of interest to you (well, besides this guide of course).

[[ChIntroHomepage]]

==== Website

You will find lots of useful information on the Wireshark homepage at
{wireshark-main-url}.

[[ChIntroWiki]]

==== Wiki

The Wireshark Wiki at {wireshark-wiki-url} provides a
wide range of information related to Wireshark and packet capture in general.
You will find a lot of information not part of this user's guide. For example,
there is an explanation how to capture on a switched network, an ongoing effort
to build a protocol reference and a lot more.

And best of all, if you would like to contribute your knowledge on a specific
topic (maybe a network protocol you know well) you can edit the wiki pages by
simply using your web browser.

[[ChIntroQA]]

==== Q&amp;A Site

The Wireshark Q&amp;A site at {wireshark-qa-url} offers a resource where
questions and answers come together. You have the option to search what
questions were asked before and what answers were given by people who
knew about the issue. Answers are graded, so you can pick out the best
ones easily. If your question hasn't been discussed before you can post
one yourself.

[[ChIntroFAQ]]

==== FAQ

The Frequently Asked Questions lists often asked questions and their
corresponding answers.

[NOTE]
.Read the FAQ
====
Before sending any mail to the mailing lists below, be sure to read the FAQ. It
will often answer any questions you might have. This will save yourself and
others a lot of time. Keep in mind that a lot of people are subscribed to the
mailing lists.
====

You will find the FAQ inside Wireshark by clicking the menu item Help/Contents
and selecting the FAQ page in the dialog shown.

An online version is available at the Wireshark website at
{wireshark-faq-url}. You might prefer this online version, as it's
typically more up to date and the HTML format is easier to use.

[[ChIntroMailingLists]]

==== Mailing Lists

There are several mailing lists of specific Wireshark topics available:

_wireshark-announce_::
    This mailing list will inform you about new program releases, which usually
    appear about every 4-8 weeks.

_wireshark-users_::
    This list is for users of Wireshark.  People post questions about building
    and using Wireshark, others (hopefully) provide answers.

_wireshark-dev_::
    This list is for Wireshark developers. If you want to start
    developing a protocol dissector, join this list.

You can subscribe to each of these lists from the Wireshark web site:
{wireshark-mailing-lists-url}. From there, you can choose which mailing
list you want to subscribe to by clicking on the
Subscribe/Unsubscribe/Options button under the title of the relevant
list.  The links to the archives are included on that page as well.

[TIP]
.The lists are archived
====
You can search in the list archives to see if someone asked the same question
some time before and maybe already got an answer. That way you don't have to
wait until someone answers your question.
====

==== Reporting Problems

[NOTE]
====
Before reporting any problems, please make sure you have installed the latest
version of Wireshark.
====


When reporting problems with Wireshark please supply the following information:

. The version number of Wireshark and the dependent libraries linked with it,
  such as Qt or GLib. You can obtain this from Wireshark's about box or the
  command `wireshark -v`.

. Information about the platform you run Wireshark on.

. A detailed description of your problem.

. If you get an error/warning message, copy the text of that message (and also a
  few lines before and after it, if there are some) so others may find the
  place where things go wrong. Please don't give something like: "I get a
  warning while doing x" as this won't give a good idea where to look.

[NOTE]
.Don't send large files
====
Do not send large files (&gt; 1 MB) to the mailing lists. Just place a note that
further data is available on request. Large files will only annoy a lot of
people on the list who are not interested in your specific problem. If required
you will be asked for further data by the persons who really can help you.
====

[WARNING]
.Don't send confidential information!
====
If you send capture files to the mailing lists be sure they don't contain any
sensitive or confidential information like passwords or personally identifiable
information (PII).
====

==== Reporting Crashes on UNIX/Linux platforms

When reporting crashes with Wireshark it is helpful if you supply the traceback
information along with the information mentioned in "Reporting Problems".

You can obtain this traceback information with the following commands on UNIX or
Linux (note the backticks):

----
$ gdb `whereis wireshark | cut -f2 -d: | cut -d' ' -f2` core >& backtrace.txt
backtrace
^D
----

If you do not have `gdb` available, you will have to check out your operating system's debugger.

Mail `backtrace.txt` to mailto:{wireshark-dev-list-email}[].

==== Reporting Crashes on Windows platforms

The Windows distributions don't contain the symbol files (.pdb) because they are
very large. You can download them separately at
{wireshark-main-url}download/win32/all-versions/ and
{wireshark-main-url}download/win64/all-versions/ .

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