#----------------------------------------------------------
#  Process command line options.
#----------------------------------------------------------
GetOptions(
    "userid=s"               => \$userid,
    "passwd=s"               => \$passwd,
    "tr_file|file|qt_file=s" => \$in_file,
    "port=s"                 => \$port,
    "log|log_fl:s"           => \$log_file,
    "verbosity|verbose:s"    => \$verbosity,
    "help|usage"             => \$usage,
);

#----------------------------------------------------------
#  Validate command line arguments.
#----------------------------------------------------------
validate_arguments()
  or pod2usage(
    -message => 'Incorrect usage!!',
    -exitval => 2,                 
    -verbose => 1,                 
    -output  => \*STDOUT,
    -noperldoc => 0
  );

#----------------------------------------------------------
#  Open up a TCP socket and start waiting for the connection request.
#----------------------------------------------------------

# Create our socket.
$logger->debug("Making the socket.");
socket( SERVER, PF_INET, SOCK_STREAM, getprotobyname('tcp') );
$logger->debug("Socket made.");

# Set socket properties.
$logger->debug("Setting socket options: SO_REUSEADDR.");
setsockopt( SERVER, SOL_SOCKET, SO_REUSEADDR, 1 );
$logger->debug("Socket options set.");

# Bind the socket to our port and all ip's.
$logger->debug( "Binding the socket to the specified port $port "
      . 'and all available IP addresses on the machine.' );
$my_addr = sockaddr_in( $port, INADDR_ANY );
unless ( bind( SERVER, $my_addr ) ) {

    $logger->fatal("Couldn't bind to $port on this machine. $!");
    $logger->fatal('Exiting with an exit code of 1.');

    exit(1);
}
$logger->debug("Binding to port $port successful.");

# Initialize our listen queue before getting ready for passive open.
$logger->debug('Initialize our listen queue. Setting queue depth to SO
+MAXCONN');
unless ( listen( SERVER, SOMAXCONN ) ) {
    $logger->fatal("Could not initialize listen'er queue for our socke
+t: $!");
    $logger->fatal('Will exit out with an exit code of 1.');

    exit(1);
}

#----------------------------------------------------------
#  Now wait for client requests.
#----------------------------------------------------------
# Cool now lets wait for the SYN from client. (We do a passive open).
REQUEST:
while ( accept( CLIENT, SERVER ) ) {

    # We got a request.
    my ( $client_port, $client_ip_address );
    my $client_sockaddr = getpeername(CLIENT);
    ( $client_port, $client_ip_address ) = sockaddr_in($client_sockadd
+r);
    $client_ip_address = inet_ntoa($client_ip_address);
    $logger->info(
        'Got a connection from ' . $client_ip_address . ':' . $client_
+port );

    # Let's clone off a copy of ourselves and get ready to accept()
    # another client request.
    if ( $child_pid = fork() ) {

        # You are in the parent here.
        close CLIENT;
        next REQUEST;
    }

    # Check if the fork succeeded.
    unless ( defined($child_pid) ) {

        # Well it did not!!!
        $logger->fatal("Could not fork () a child. $!");
        $logger->fatal('Exiting with a status of 1');

        # What do we do with children who are already fork()'d?
        exit(1);

    }
    # Fork'd ok!! We are in the child SoupTCP server.
    $logger->debug(
        'Child PID:' . $$ . ' - Closing off unwanted filehandle SERVER
+.' );
    close(SERVER);

    # Keep our pipes piping hot.
    $logger->debug( 'Child PID:' . $$
          . ' - Flushing filehandle CLIENT after every write.' );
    CLIENT->autoflush(1);

    #------------------------------------------
    # This info gets to the client!!
    #------------------------------------------
    print CLIENT 'Before READING DATA' . "\n";

    # The reading should stop once we hit a line-feed.
    local $/ = '\x0A';

    # The first packet we expect from the client is a Login Request pa
+cket.
    $client_data = <CLIENT>;
    
    #------------------------------------------    
    # This info never gets to the client. (Buffered) OR
    # The process never reaches this point and blocks on <CLIENT>.
    # How do I debug it? Should I use sysread (and syswrite)? But then
+ it reads
    # fixed length packets and I am getting variable length data packe
+ts!!
    #------------------------------------------
    print CLIENT 'After READING DATA' . "\n";
[download]

local $/ = '\x0A';
should be
local $/ = "\x0A";

It's waiting for the 4 char sequence "\", "x", "0", "A", but it never receives it.

Next time, please provide something runnable.

Many Thanks to Ikegami!! Learnt a lot from here. I also replumbed the code using IO::Socket::INET. Cheers!!