gistfile1.pl

    require Parse::Netstat;
 
    my $timer; $timer = AnyEvent->timer(
        interval => 0.6,
        cb => sub {
            my $netstat;
            AnyEvent::Util::run_cmd(
                'LANG=C netstat --inet --inet6 -n -p -l',
                '>' => \$netstat,
                '2>' => \(my $dummy),
            )->cb(sub {
                my $stat = Parse::Netstat::parse_netstat(output => $netstat);
                for (@{$stat->[2]->{active_conns} or []}) {
                    next unless defined $_->{pid};
                    if ($_->{pid} == $pid and
                        $_->{local_port} == $port and
                        $_->{state} eq 'LISTEN') {
                        $cv_start->send;
                        undef $timer;
                        last;
                    }
                }
            });
        },
    );