#-------------------------------------------------------------------------
#SERVER SCRIPT
#!/usr/bin/perl -Tw
require 5.002;
use Socket;
#- ReverseEchoer.pl ((c) 1999 Dr. Herong Yang example)
$domain = 2; # Internet domain
$type = 1; # Sequenced, reliable, two-way connection, byte streams
socket(SOCK, PF_INET, SOCK_STREAM, getprotobyname('tcp'));
$host = pack('C4', 0, 0, 0, 0); # Local wildcard host id: 0.0.0.0
$port = 7654;
$address = pack('S n a4 x8', $domain, $port, $host);
bind(SOCK, $address);
$queueSize = 5; # Queue up to 5 connections
listen(SOCK, $queueSize);
$cAddress = accept(NEWSOCK, SOCK);
($cDomain, $cPort, $cHost) = unpack('S n a4 x8', $cAddress);
select(NEWSOCK); $| = 1; select(STDOUT);
print NEWSOCK "Welcome to Reverse Echo Server.\r\n"; ##### print this to the client (COMMENT 1)
while ($m=<NEWSOCK>) { ##### wait for input from client, but nothing ever comes (COMMENT 5)
  $m =~ s/\n|\r//g;
  last if ($m eq ".");
  $m = reverse($m);
  print NEWSOCK "$m\r\n";
}
close(NEWSOCK);
#-------------------------------------------------------------------------
#CLIENT SCRIPT
#!/usr/bin/perl -w
require 5.002;
use strict;
use Socket;
my ($remote, $port, $iaddr, $paddr, $proto, $line, $m);
$remote = shift || 'localhost';
$port = shift || 7654;
if ($port =~ /\D/) { $port = getservbyname($port, 'tcp') }
die "No port" unless $port;
$iaddr = inet_aton($remote) or die "no host: $remote";
$paddr = sockaddr_in($port, $iaddr);
$proto = getprotobyname('tcp');
socket(SOCK, PF_INET, SOCK_STREAM, $proto) or die "socket: $!";
connect(SOCK, $paddr) or die "connect: $!";
while ($line = <SOCK>) {
  print $line; ##### the Welcome line appears here        (COMMENT 2)
  $m = <STDIN>; ##### I type "abc" here...                (COMMENT 3)
  print SOCK $m; ##### ...send it to the server socket script (COMMENT 4)
}
close(SOCK) or die "close: $!";