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LISTEN(1)                  Linux Programmer's Manual                 LISTEN(1)



NAME
       listen(1,2,7) - monitor AX.25 traffic

SYNOPSIS
       listen(1,2,7) [-8] [-a] [-c] [-h] [-i] [-p port] [-r] [-t] [-v]

DESCRIPTION
       Listen  uses SOCK_PACKET facilities to provide a network monitor of all
       AX.25 traffic heard by the system. Since KISS is implicitly promiscuous
       no special driver configurations are needed.

       This  version(1,3,5)  displays standard AX.25, PE1CHL extended AX.25, NET/ROM,
       Rose, ARP, IP, ICMP, TCP and UDP. It also displays IP, TCP,  ICMP,  TCP
       and  UDP  encapsulated within NET/ROM frames. The program also displays
       AX.25 and IP encapsulated within an IP frame, but see RFC1326 for  rea-
       sons not to do so.

       Listen  makes  an  attempt  at decoding some of the more common routing
       protocols. RSPF and RIP (both "normal" and G8BPQs  RIP98)  are  traced.
       JNOS style NET/ROM node polls are also displayed.

       Listen  can  use  colors  to make the output more readable. The ncurses
       library is used to accomplish this.  Color support  defaults  to  being
       disabled, and the -c parameter is used to enable it.

OPTIONS
       -8        Indicates  that  the  terminal  is  capable of printing 8-bit
                 characters. This parameter is required for the  -i  parameter
                 to work.

       -a        Allow for the monitoring of outgoing frames as well as incom-
                 ing ones.

       -c        Enable color support.

       -h        Dump the data portion of the packet in(1,8) both  hexadecimal  and
                 ASCII. The default is to display data as ASCII only.

       -i        Map  IBM codepage 437 characters 128-158 to their ISO-Latin-1
                 equivalents.  This is a hack  for  scandinavian  users.  This
                 parameter  is only valid when used with the -8 and -c parame-
                 ters.

       -p port   Monitor only those frames received on a particular  port,  by
                 default all AX.25 devices are monitored.

       -r        Dump  the data portion in(1,8) a "readable" fashion, which is more
                 suitable for tracing plaintext AX.25 traffic.  CR-LF  conver-
                 sion is done.

       -t        Displays a timestamp with each packet received.

       -v        Display the version.

FILES
       /etc/ax25(3,4)/axports

SEE ALSO
       call(1),  mheard(1),  beacon(1),  ax25(3,4)(4),  netrom(4), rose(3,4)(4), kissat-
       tach(8).


BUGS
       Listen does not validate the checksums of frames that support them  (ie
       IP),  therefore corrupt frames will be displayed with bogus values. The
       MSS of a TCP frame that contains that option is not displayed.

AUTHORS
       Alan Cox GW4PTS <alan@cymru.net>
       Jonathan Naylor G4KLX <g4klx@g4klx.demon.co.uk>
       Phil Karn KA9Q <karn@qualcomm.com>
       Heikki Hannikainen OH7LZB <hessu@pspt.fi>



Linux                           27 August 1996                       LISTEN(1)

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