# server sends to client
<command name="get_passwd">
 Please enter your password:
</command>

# client sending to server
<command name="text_data">
 example_password
</command>

##</code><code>##

# server sends to client.
syswrite(
 $client,
 "10get_passwd0027Please enter your password:"
);

# client reads from server
my ($len, $cmd, $data);
sysread($server, $len, 2);
sysread($server, $cmd, $len);
sysread($server, $len, 4);
sysread($server, $data, $len);

# $cmd  eq 'get_passwd'                  # this is
# $data eq 'Please enter your password:' # correct, right?