UDP is connectionless so you probably won't be able to send/receive on a single socket pair (bi-directional). Have you tried opening a listening socket on port 58255 (LocalPort) and having that 'recv' the response as it will be unicast to you? For example

use strict;
use warnings;

[...]

my $FindCard = IO::Socket::INET->new(Proto=>"udp",LocalPort=>58255,Pee
+rPort=>55777,PeerAddr=>"192.168.11.255",Broadcast=>1)
or die "Can't make UDP socket: $@"; 

my $recv = IO::Socket::INET->new(Proto=>"udp",LocalPort=>58255)
or die "Can't make UDP socket: $@"; 

[...]

$FindCard->send("");
$recv->recv($datagram,120,$flags);

[...]
[download]