You probably you forgot to turn on the 'tcp_service_check' option. If it's turned off (which it is by default) then ping will report success if it gets an explicit "connection denied" from the server (since that means the server is up -- otherwise it couldn't have denied the connection)

However, you don't want to check if the server itself is up but if a specific service is up, so a refused connection is a failure to you. If you turn on 'tcp_service_check', Net::Ping will only report success if it could actually establish a connection, and report failture if the connection was denied.

Example:

use strict;
use warnings;
use Net::Ping;

my $p = Net::Ping->new('tcp');
$p->tcp_service_check(1);

my $host = "192.168.100.12";
my $port = 80;

$p->{'port_num'} = $port;
print "The service on $host port $port is ",
        ($p->ping($host) ? "up" : "down"), ".\n";
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•Update: Note that the tcp_service_check option isn't available in the Net::Ping that is included with perl 5.8.0, however it is available in the latest version.