Hm. Did you write this code?

This might work or it might not. I cannot test it so you will have to and solve whatever problems you encounter.

Try adding the subroutine I posted above to the script.And then replace this chunk of code:

                # obtient la réponse
                eval {
                    local $SIG{ALRM} = sub { die "temporisation de l'a
+larme" };
                    alarm $RECV_TIMEOUT;
                    $portaddr = recv($sock, $packet, 1500, 0) 
                       or die "Réception impossible: $!";
                    alarm 0;
                    1;
                } or die($@);
                # affiche la sortie
[download]

with:

                # obtient la réponse
                my(undef,undef,$packet) = recv_timeout( $sock, $RECV_T
+IMEOUT );
                die "temporisation de l'alarme" } unless $packet;
                # affiche la sortie
[download]