Structure
=========

Offset  Size   Type  Description
 0      4      data  protocol tag, must be 0xFB1AB1AF
 4      2      uint  sequence number
 6      2      uint  sequence ack
 8      4      data  bitfield with previous acks
12      1      uint  type code for the payload
13      3      none  padding, reserved for future use
16      0-484  data  payload, contents and length vary,
                     mostly depending on the type code

all multibyte values are in LE
the current code does no conversion, so only works on machines
with native LE (or BE if the server and all clients are on that,
but that's by accident and will break if conversion code is ever
added)

Common Types
------------

Name          Size  Type
vec3          12    3x 32bit float
vec3i         12    3x 32bit signed int
quat          16    4x 32bit float
entity state  64    vec3i, vec3, vec3, quat, vec3


Packets
=======

Ping
----

To tell the other side we're still alive.
Both server and client will send this if they haven't sent something in
a while.

Code: 0
Payload: none
Length: 0


Login
-----

Sent from client to serveri as a request to join. The server may
respond negatively if the player name is already taken or some cap has
been reached.

Code: 1
Payload:
	0 player name, max 32 byte UTF-8 string,
	  shorter names should be zero terminated
Length: 0-32


Join
----

Sent by the server either as a response to a successful login or when
it's changing worlds.

Code: 2
Payload:
	 0 entity ID of the player, 32bit unsigned int
	 4 entity state of the player
	68 name of the world the server's currently running
	   max 32 byte UTF-8 string
Length: 68-100


Part
----

Sent by the server either as a respons to a failed login or when the
client was kicked.
Optionally sent by the client on disconnect.

Code: 3
Payload: none
Length: 0


Player Update
-------------

Sent by clients to notify the server of their changes to the player.

Code: 4
Payload:
	 0 entity state of the player as seen by the client
Length: 64


Spawn Entity
------------

Sent by the server to notify the client of an entity entering spawn range.

Code: 5
Payload:
	  0 entity ID, 32bit unsigned int
	  4 entity's skeleton ID, 32bit unsigned int
	  8 entity state
	 72 bounding box of the entity, 6x 32bit float
	 96 flags, 32bit bitfield with boolean values
	    1: world collision
	100 entity name, max 32 byte UTF-8 string
Length: 132


Despawn Entity
--------------

Sent by the server to notify the client of an entity leaving spawn range.

Code: 6
Payload:
	0 entity ID, 32bit unsigned int
Length: 4


Entity Update
-------------

Sent by the server to notify the client of updated entity properties.
Contained entities must be ordered by ascending entity ID.

Code: 7
Payload:
	 0 number of entities, 32bit int, 1-7
	 4 entity ID, 32bit unsigned int
	 8 entity state
	72 next entity...
Length: 4 + multiple of 68, max 452


Player Correction
-----------------

Sent by the server to tell a client that its prediction is way off.

Code: 8
Payload:
	 0 sequence number of the offending packet, 16bit unsigned int
	 2 entity state of the player's entity on the server
Length: 66