The Cow Game
============

You are trying to guess a 4-nybble sequence.  Each nybble will have
either 1 or 2 bits set, and the highest bit will never be set.  The
game server will tell you how many nybbles in each guess were correct,
and how many had one correct bit.  It does not tell you which
positions



The Cow Client
==============

The client connects to the Cow server running on the IPv6 address
provided in argument 1.  If argument 2 is present, the client will
try to run it, providing stdin and stdout as in interactive mode.

In interactive mode (no argument 2), the client reads a guess in the
form of 4 ASCII numerals, and prints the number of correct nybbles
followed by the number of nybbles with one correct bit.

Here is an example of a session:

    1111
    12
    2222
    10
    4444
    02
    4244
    12
    1244
    22
    1255
    cow:xylep-radar-nanox



The Cow Protocol
================

cowd runs on port 3782.

The client always sends 6 octets.  To request a new session, it sends
all zeroes.  Otherwise it sends the 4-octet game identifier provided
by the server, concatenated with a 2-octet guess.

The server will respond with a new game identifier (4 octets) to a new
game request or if the game requested is too old.  If a guess is
incorrect, the server will respond with either a 1-octet score in
which the high nybble is the number of correct nybbles in the guess,
and the low nybble is the number of nybbles in the guess with one
correct bit.  If a guess is correct, the server will respond with a
token of length 5 octets or more.

There are multiple tokens, one per number of guesses used, up to
some maximum number of guesses defined per server instance.