use strict;  
use IO::Socket;

my $socket=IO::Socket::INET->new(LocalAddr => 'localhost',
                                 LocalPort => 2224,
                                 Proto     => 'udp')
  or die "socket: $!";

while ((my $length=sysread($socket, my $buffer, 65536)) != 0)
  {
    die "sysread: $!" if (!defined($length));
    # $buffer contains the received packet
  }                        

##</code><code>##

use strict;
use IO::Socket;

my $socket=IO::Socket::INET->new(PeerAddr => 'localhost',
                                 PeerPort => 2224,
                                 Proto     => 'udp')
  or die "socket: $!";

syswrite($socket, "Hello, there\n");

##</code><code>##

my $length;
while (defined($length=sysread($socket, my $buffer, 65536)) && $length != 0)
  { ... }
die "sysread: $!" if (!defined($length));