If a UDP socket has an address bound to it, then ICMP errors related to that that socket are passed back to it, eg

use IO::Socket;

use strict;  use warnings;

my $sock = IO::Socket::INET->new(
    PeerAddr => 'localhost:9999',
    Proto=>'udp',
    
    )
or die "sock new: $!\n";
my $result;
$sock->send("abc",0) or die "send: $!\n";
defined($sock->recv($result,1,0)) or die "recv: $!\n";
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For a destination port that isn't open, this code outputs:

recv: Connection refused
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Dave.