Perl : scan a list of networks, looking for hosts responding on the port 80 (http) (See related posts)

use strict;
use Net::Ping;
use IO::Socket::INET;

sub isodate() {
        my ($day, $mon, $year, $hour, $min, $sec) = (localtime)[3, 4, 5, 2, 1, 0];
        $mon++; # 0-based index
        $year = $year + 1900;
        my $date = sprintf ("%04i-%02i-%02i %02i\:%02i\:%02i", $year, $mon, $day, $hour, $min, $sec);
        return $date;
}

sub testhost {
       my $p = new Net::Ping("tcp");
       $p->{port_num}=80; 
       my @result = $p -> ping($_[0],2);
       return $result[0];
       }

sub to_dot {
	my $n = shift;
	my @decimal;
	for (1..4) {
		unshift @decimal, $n & 0xFF;
		$n >>= 8;
	}
	return join(".",@decimal);
}

my %dejavu;
open FH,"liste.txt";
while (<FH>) {
	chomp;
	my ($routeur,$mask)=split;
	
	next if $routeur !~ /\d+\.\d+\.\d+\.\d+$/ or $mask !~ /\d+\.\d+\.\d+\.\d+$/;
	
	next if defined($dejavu{$routeur});
	$dejavu{$routeur}=1;
	
	my ($o1,$o2,$o3,$o4) = split /\./,$mask;
	my $mask=$o1*256**3+$o2*256**2+$o3*256+$o4;
	my $num = $mask ^ 0xFFFFFFFF;
	$num--;

	my ($o1,$o2,$o3,$o4) = split /\./,$routeur;
	my $net=$o1*256**3+$o2*256**2+$o3*256+$o4 & $mask;
	
	#print join("|",$routeur,&to_dot($net),$num)."\n";
	
	print "Starting scanning network ".to_dot($net).", router = ".$routeur."\n";
	print "Adresses demarrant de ".to_dot($net+1)." et finissant a ".to_dot($net+$num).".\n";
	for my $i (1..$num) {
		my $host=to_dot($net+$i);
		if ( &testhost($host) ) {
			print "$host is alive\n";
			my $port=80;
			my $sock = new IO::Socket::INET (PeerAddr => $host,
					     PeerPort => $port,
					     Proto => 'tcp');
			if ($sock){
				close $sock;
				print "$port -open on $host\n";
				open OUT,">>webservers.txt";
				print OUT join("|",isodate(),$host,to_dot($net),$routeur)."\n";
				close OUT;
			}	else	{
				print "$port -closed on $host\n";
			}

		} else {
			print "$host is not responding\n";
		}
	}
}


close FH;