#! /usr/local/bin/perl

# xtcptrace - a tcpdump "wrapper" to decode X KeyCodes
# Dave Plonka <plonka@doit.wisc.edu>, Aug 27  1998
#
# Affected:
#   Digital Unix 4.0E
#   SuSE Linux 6.1
#   Red Hat Linux 6.0
#   Solaris 2.6

$tcpdump='/path/to/tcpdump';

if (! -x ${tcpdump}) {
   print STDERR "You don't seem to have execute permission on \"${tcpdump}\".\n";
   exit 1
}

# X KeyCodes...  These can be determined using xkeycaps(1), for example.
# I assume these are well documented somewhere.
# Remember we're watching key presses here, not the resulting X KeySym or
# ASCII character.  So a '[SHIFT]' preceeding an 'A' is probably a capital
# letter A, etc.
%code = (
0x0A => '1', 0x0B => '2', 0x0C => '3', 0x0D => '4',
0x0E => '5', 0x0F => '6', 0x10 => '7', 0x11 => '8',
0x12 => '9', 0x13 => '0', 0x26 => 'A', 0x38 => 'B',
0x36 => 'C', 0x28 => 'D', 0x1A => 'E', 0x29 => 'F',
0x2A => 'G', 0x2B => 'H', 0x1F => 'I', 0x2C => 'J',
0x2D => 'K', 0x2E => 'L', 0x3A => 'M', 0x39 => 'N',
0x20 => 'O', 0x21 => 'P', 0x18 => 'Q', 0x1B => 'R',
0x27 => 'S', 0x1C => 'T', 0x1E => 'U', 0x37 => 'V',
0x19 => 'W', 0x35 => 'X', 0x1D => 'Y', 0x34 => 'Z',
0x40 => '[ALT]', 0x41 => ' ', 0x42 => '[CAPS LOCK]', 0x32 => '[SHIFT]',
0x24 => '[RETURN]', 0x16 => '[BACK SPACE]',
);

open(STDIN, "${tcpdump} -l -x -s 65535 -v @ARGV|") || die;
select(STDIN); $| = 1;
select(STDOUT); $| = 1;
while (<STDIN>) {
   # This is a total kludge below - we only look at 32 byte packets since
   # that is the size of an xEvent.  However, we may miss some events because
   # they can be grouped together in one packet.  So really, any multiple of
   # 32 (e.g. 64, 96) could also contain xEvents.
   if (m/^\d\d:\d\d:\d\d\.\d+\s+.*\.6000\s+>\s+.*\(32\)/) {
      scalar(<STDIN>); # discard
      scalar(<STDIN>); # discard
      $_ = scalar(<STDIN>);
[2000]# Another kludge - the magic numbers in the line below (0x5018,  0x7d78,
[2000]# etc.) were discovered by watching xEvents with tcpdump(1).  I don't
[2000]# know that they'll have those values from all X servers or what.
[2000]# Probably, the xEvent typedef struct, as defined in <X11/Xproto.h>,
[2000]# should be grokked to implement this correctly.
[2000]# The Right Thing(tm) would probably be to pack the packet content as
[2000]# a 32-byte scalar, then unpack it into it's appropriate structure
[2000]# members.
      if (m/5018\s+7d78\s+[0-9a-f][0-9a-f][0-9a-f][0-9a-f]\s+0000\s+03([0-9a-f][0-9a-f])/) {
	 if ($c = $code{hex($1)}) {
	    print "$c\n"
	 } else {
	    print "KeyCode 0x$1\n"
	 }
      }
   }
}

exit
#                 www.hack.co.za           [2000]#