=head1 NAME

Ethereal - Interactively browse network traffic

=head1 SYNOPSYS

B<ethereal>
S<[ B<-B> byte view height ]>
S<[ B<-b> bold font ]>
S<[ B<-c> count ]>
S<[ B<-h> ]>
S<[ B<-i> interface ]> 
S<[ B<-m> font ]>
S<[ B<-n> ]>
S<[ B<-P> packet list height ]>
S<[ B<-r> infile ]>
S<[ B<-s> snaplen ]>
S<[ B<-T> tree view height ]>
S<[ B<-t> time stamp format ]>
S<[ B<-v> ]>
S<[ B<-w> savefile]>

=head1 DESCRIPTION

B<Ethereal> is a network protocol analyzer based on the B<GTK+> GUI toolkit.  It lets
you interactively browse packet data from a live network or from a B<pcap>
/ B<tcpdump()> formatted capture file.

=head1 OPTIONS

=over 4

=item -B

Sets the initial height of the byte view (bottom) pane

=item -b

The bold font name used for packet fied display.

=item -c

The default number of packets to read when capturing live data.

=item -h

Prints the version and options and exits.

=item -i

The name of the interface to use for live packet capture.  It should match
one of the names listed in "B<netstat -i>" or "B<ifconfig -a>".

=item -m

The font name used by B<Ethereal>.

=item -n

Disable network object name resolution (such as hostname, TCP and UDP port
names).

=item -P

Sets the initial height of the packet list (top) pane

=item -r

Read packet data from I<file>.  Currently, B<Ethereal> only understands
B<pcap> / B<tcpdump> formatted files.

=item -s

The default snapshot length to use when capturing live data.  No more than
I<snaplen> bytes of each network packet will be read into memory, or saved
to disk.

=item -T

Sets the initial height of the tree view (top) pane

=item -t

Sets the format of the packet timestamp displayed in the packet list
window.

=item -v

Prints the version and exits.

=item -w

Sets the default capture file name.

=back

=head1 INTERFACE

=head2 MENU ITEMS

=over 4

=item File:Open, File:Close

Open or close a capture file.

=item File:Print Packet

Print a description of each protocol header found in the packet, followed
by the packet data itself.  Printing options can be set with the
I<Edit:Menu Options> menu item.

=item File:Quit

Exits the application.

=item Edit:Printer Options

Sets the packet printing options (see L<"Printer Options"> below).

=item Tools:Capture

Initiates a live packet capture (see L<"Capture Preferences"> below).

=item Tools:Filter

Sets the filter preferences (see L<"Filters"> below).

=back

=head2 WINDOWS

=over 4

=item Main Window

The main window is split into three sections.  You can resize each section
using a "thumb" at the right end of each divider line.  An informational
message is also displayed at the bottom of the main window.

The top section contains the list of network packets that you can scroll
through and select.  The packet number, packet timestamp, source and
destination addresses, protocol, and description are printed for each
packet.  An effort is made to display information as high up the protocol
stack as possible, e.g. IP addresses are displayed for IP packets, but the
MAC layer address is displayed for unknown packet types.

The middle section contains a I<protocol tree> for the currently-selected
packet.  The tree displays each field and its value in each protocol header
in the stack.

The bottom section contains a hex dump of the actual packet data. 
Selecting a field in the I<protocol tree> highlights the appropriate bytes
in this section.

=item Printer Options

The I<Printer Options> dialog lets you select the output format of packets
printed using the I<File:Print Packet> menu item.

The radio buttons at the top of the dialog allow you choose between 
printing the packets as text or PostScript, and sending the output
directly to a command or saving it to a file.  The I<Command:> text entry
box is the command to send files to (usually B<lpr>), and the I<File:>
entry box lets you enter the name of the file you wish to save to. 
Additinally, you can select the I<File:> button to browse the file system
for a particular save file.

=item Capture Preferences

The I<Capture Preferences> dialog lets you specify various parameters for
capturing live packet data.

The I<Interface:> entry box lets you specify the interface from which to
capture packet data.  The I<Count:> entry specifies the number of packets
to capture.  Entering 0 will capture packets indefinitely.  The I<File:>
entry specifies the file to save to, as in the I<Printer Options> dialog
above.  You can choose to open the file after capture, and you can also
specify the maximum number of bytes to capture per packet with the
I<Capture length> entry.

=item Filters

The I<Filters> dialog lets you create and modify filters, and set the
default filter to use when capturing data or opening a capture file.

The I<Filter name> entry specifies a descriptive name for a filter, e.g.
B<Web and DNS traffic>.  The I<Filter string> entry is the text that
actually describes the filtering action to take.  It must have the same
format as B<tcpdump> filter strings, since both programs use the same
underlying library.  A filter for HTTP, HTTPS, and DNS traffic might look
like this:

  tcp port 80 or tcp port 443 or port 53

The dialog buttons perform the following actions:

=over 8

=item New

If there is text in the two entry boxes, it creates a new associated list
item.

=item Change

Modifies the currently selected list item to match what's in the entry
boxes.

=item Copy

Makes a copy of the currently selected list item.

=item Delete

Deletes the currently selected list item.

=item OK

Sets the currently selected list item as the active filter.  If  nothing
is selected, turns filtering off.

=item Save

Saves the current filter list in F<$HOME/.ethereal/filters>.

=item Cancel

Closes the dialog without making any changes.

=head1 SEE ALSO

L<tcpdump(1)>, L<pcap(3)>

=head1 NOTES

The latest version of B<ethereal> can be found at
B<http://ethereal.zing.org>.

=head1 AUTHORS

  Original Author
  -------- ------
  Gerald Combs  <gerald@zing.org>


  Contributors
  ------------
  Gilbert Ramirez Jr.  <gram@verdict.uthscsa.edu>
  Hannes R. Boehm      <hannes@boehm.org>
  Mike Hall            <mlh@io.com>
  Bobo Rajec           <bobo@bsp-consulting.sk>
  Laurent Deniel       <deniel@worldnet.fr>
  Don Lafontaine       <lafont02@cn.ca>


Alain Magloire <alainm@rcsm.ece.mcgill.ca> was kind enough to give his
permission to use his version of snprintf.c.

Dan Lasley <dlasley@promus.com> gave permission for his dumpit() hex-dump
routine to be used.