# Like tcp protocol, but with many hosts
    $p = Net::Ping->new( "syn" );
    $p->port_number( getservbyname( "http", "tcp" ) );


    ### send all the pings first
    foreach $host ( @host_array ) {
      $p->ping( $host );
    }

    ### Then check which hosts responded.
    while( ( $host, $rtt, $ip ) = $p->ack ) {
      print "HOST: $host [$ip] ACKed in $rtt seconds.\n";
    }