#!/usr/bin/perl -w
use strict;
use IO::Socket;
my $sock = new IO::Socket::INET(
                   LocalHost => 'localhost',
                   LocalPort => 7890,
                   Proto     => 'tcp',
                   Listen    => SOMAXCONN,
                   Reuse     => 1);
$sock or die "no socket :$!";
STDOUT->autoflush(1);

my $req_name = "Enter Name: \n";
my $req_pass = "Enter Password: \n";
my $req_none = "Enter \n";

sub verify_passw {
    my ($name, $pass) = @_;
    # print STDERR "name=$name, pass=$pass\n";  # debug
    # ...
    return 1;
}

while (my $new_sock = $sock->accept())
{
    my $name = "";  # lifetime is connection
    my $auth = 0;   # ditto (storing state of session)

    while (<$new_sock>)
    {
        /^HELLO$/ and print($new_sock $req_name), next;
     
        /^NAME: (\w*)/ and do {
            $name = $1;
            if ($name && length($name)<=8) {
               print $new_sock "Ok, name: $name\n";
               print $new_sock $req_pass;
            } else {
               print $new_sock "Invalid name: '$name'\n";
               print $new_sock $req_name;
            }
            next
        };

        /^PASS: (\w*)/ and do {
            my $pass = $1;
            if ($auth = verify_passw($name, $pass)) {  # =, not ==
               print $new_sock "Login ok\n";
               print $new_sock $req_none;
            } else {
               print $new_sock "Invalid password!\n";
               print $new_sock $req_pass;
            }
            next
        };
          
        /^DATE$/  and print($new_sock scalar(localtime), "\n"), next;
    
         print $new_sock "DEFAULT\n";
    }
    close $new_sock;
}

##</code><code>##

#!/usr/bin/perl -w
use strict;
use IO::Socket;
my $host = shift || 'localhost';
my $port = shift || 7890;
my $sock = new IO::Socket::INET(
                  PeerAddr => $host,
                  PeerPort => $port,
                  Proto    => 'tcp');
$sock or die "no socket :$!";


my %handler = (
    Name     => \&name,
    Password => \&pass,
);

sub show_reply_and_next {
    do {
        $_=<$sock>;
        print unless /Enter $/;
    } until /^Enter (\w*)/;

    # $1 holds what to do next
    if ($handler{$1}) {
        $handler{$1}->();
    }
    # else just return
}

sub hello {
    print $sock "HELLO\n";
    show_reply_and_next();
}

sub name {
    my $name = <STDIN>;
    print $sock "NAME: $name";
    show_reply_and_next();
}

sub pass {
    my $pass = <STDIN>;
    print $sock "PASS: $pass";
    show_reply_and_next();
}

###

hello();   # initiates login

print $sock "DATE\n";
print scalar <$sock>;

print $sock "NONE\n";
print scalar <$sock>;

close $sock;

##</code><code>##

$ ./827156_client.pl
Enter Name: 
toooooooo_long
Invalid name: 'toooooooo_long'
Enter Name: 

Invalid name: ''
Enter Name: 
almut
Ok, name: almut
Enter Password: 
foobar
Login ok
Sun Mar  7 01:10:53 2010
DEFAULT