#! perl -slw
use strict;
use IO::Socket;

use constant {
    HEARTBEAT       => 1, ## seconds
    AREYOUTHERE     => 'Er, hello?',
    IPS             => [
        map{
            scalar sockaddr_in( $_, inet_aton( '127.0.0.1' ) )
        } 10001..10005
    ],
};

my $s = IO::Socket::INET->new( Proto => 'udp' )
    or die $!, $^E;

## Forever, slowly until time to die
while( sleep HEARTBEAT ) {
    for my $client ( 0 .. $#{ IPS() } ) {
        $s->send( "$client: " . AREYOUTHERE, 0, IPS->[ $client ] )
    }
}