#!/usr/local/bin/perl
# file: udp_echo_serv.pl
# Figure 18.4: A UDP reverse-echo server

# usage: udp_echo_serv.pl [port]

use strict;
use IO::Socket;
use constant MY_ECHO_PORT => 2007;
use constant MAX_MSG_LEN  => 5000;

my $port = shift || MY_ECHO_PORT;

$SIG{'INT'} = sub { exit 0 };

my $sock = IO::Socket::INET->new(Proto=>'udp',
                                 LocalPort=>$port) or die $@;

my ($msg_in,$msg_out);
warn "servicing incoming requests....\n";
while (1) {
  next unless $sock->recv($msg_in,MAX_MSG_LEN);
  my $peerhost = gethostbyaddr($sock->peeraddr,AF_INET) || $sock->peerhost;
  my $peerport = $sock->peerport;
  my $length   = length($msg_in);

  warn "Received $length bytes from [$peerhost,$peerport]\n";

  $msg_out = reverse $msg_in;
  $sock->send($msg_out) or die "send(): $!\n";
}

$sock->close;

__END__