use Socket;
use strict;

socket(SOCK,PF_INET,SOCK_RAW,getprotobyname('icmp')) || die $!;

my $checksum = 0;
use constant ICMP_ECHOREPLY => 0;
use constant ICMP_ECHO => 8;
use constant ICMP_STRUCT => "C2 n3";
use constant SUBCODE => 0;
use constant ICMP_FLAGS => 0;
use constant ICMP_PORT => 0;

my $seq=1;

my $msg = pack(ICMP_STRUCT,ICMP_ECHO,SUBCODE,$checksum,$$,$seq);
my $chks = &ceksum($msg);

$msg = pack(ICMP_STRUCT,ICMP_ECHO,SUBCODE,$chks,$$,$seq);
my $host = sockaddr_in(ICMP_PORT,inet_aton('192.168.0.1'));
send(SOCK,$msg,ICMP_FLAGS,$host) || warn "$! \n";

sub ceksum {
  my ($msg) = @_;
  my ($len_msg,$num_short,$short,$chk);
  $len_msg = length($msg);
  $num_short =int($len_msg/2);
  $chk = 0;
  foreach $short(unpack("n$num_short", $msg)) {
    $chk += $short;
  }
  $chk +=(unpack("C",substr($msg,$len_msg-1,1)) << 8) if $len_msg % 2;
  $chk = ($chk >> 16) + ($chk & 0xffff);
  return(~(($chk >> 16) + $chk) & 0xffff);
}


##</code><code>##

use Socket;

socket(SOCK,PF_INET,SOCK_RAW,getprotobyname('icmp')) || die "Error: $!\n";
$msg = pack("C2 n3",8,0,32127,0,1);
print "the value of checksum is:", unpack('H4', pack('n',32127)), "\n";
print "[And you should see this in your tcpdump -i lo icmp -xxx]\n";
send(SOCK,$msg,0,sockaddr_in(0,inet_aton('localhost'))) || die "Error: $! \n";