(for v3.16.2, not interested in lower)

Initial connection
------------------

Client sends bytes (signed char):
0	lib version 	(3)
1	lib subversion	(16)
2	lib patchlevel	(2)
3	flags:
	MEMB_SESSION 0x1 (wants group membership notifications)
	PRIORITY_CONN 0x10 (priority connection - recorded but ignored)
4	name length	(0-MAX_PRIVATE_NAME(10))
5-(5+namelength) name	"myname" or empty, not nul-terminated

Server may send back signed char of
	REJECT_VERSION(-7),
	REJECT_NO_NAME(-4),
	REJECT_ILLEGAL_NAME(-5),
	REJECT_NOT_UNIQUE(-6)
	and then close,

otherwise,
Server sends unsigned char of strlen of allowed auth methods (below).
Server sends allowed auths (space-separated, *space-terminated*)
Server may also immediately REJECT_AUTH(-9) and close (?!)
	(only on server config error?)

Client sends a bytearray of strings
char	auth_methods_desired[MAX_AUTH_METHODS][MAX_AUTH_NAME]
	# MAX_AUTH_NAME=30
	# MAX_AUTH_METHODS=3

[Client and server then exchange arbitrary octets for auth, null by default]

If auth failed, server sends REJECT_AUTH(-9) and closes.

Server sends bytes (one at a time) (signed chars):
	ACCEPT_SESSION(1)
	server version(3)
	server subversion(16)
	server patchlevel(2)

Server then constructs private group name #sesname#servname.
Server sends low-byte of the strlen of this name as a signed char.
Server sends private group name string (not null-terminated)

(end of initial chat)



Multicasting
------------

Client sends a header:
uint32_t	type # a REGULAR_MESS or KILL_MESS, JOIN_MESS, LEAVE_MESS
		     # via Set_endian
char		private_group_name[MAX_GROUP_NAME]
int32_t		num_groups	# count of recipient groups
int32_t		hint		# (passed through from app via
				# Set_endian((mess_type << 8) & 0x00ffff00)
int32_t		data_len	# total length of message body

Client sends groups:
char		groups[num_groups][MAX_GROUP_NAME] # array of receiving groups

Client then sequentially sends each scatter block of message body.



Receiving
---------

Server sends a header:
uint32_t	type
		# SELF_DISCARD set if the original had it set
		# (iff this is a REJECT_MESS)
char		sender[MAX_GROUP_NAME]
int32_t		num_groups
int32_t		hint	
int32_t		data_len

If type & REJECT_MESS, then server sends
uint32_t	original type of rejected message

Server sends
char		groups[num_groups][MAX_GROUP_NAME]
		# this will be modified in a REJECT_MESS
		# to append recipients private groupname

Server sends message body.


Received body specifics
-----------------------

1. If this is a transitional member message, that is
(type & TRANSITION_MESS != 0) && (type & REJECT_MESS == 0), then

in header:
hint = 0
sender = the group for which this is a notification (nul-terminated string)
num_groups = 0
groups is empty

message body is:
group_id	gid # ident of the group view (from arch.h)


2. If this is a regular membership message, that is
(type & REG_MEMB_MESS != 0) && (type & REJECT_MESS == 0), then

in header:
hint = 0
sender = the group for which this is a notification (nul-terminated string)
num_groups = number of members
groups = members' private names

message body is:
group_id	gid # ident of the group view (from arch.h)
int32		num_members # number of members in VS set
char		vs_members[num_members][MAX_GROUP_NAME]

content of vs_members defined by by flags in type:
CAUSED_BY_JOIN		new member name
CAUSED_BY_LEAVE		leaving member name
CAUSED_BY_DISCONNECT	disconnecting member name
CAUSED_BY_NETWORK	only members from previous VS set


3. If this is a self-leave membership message, that is
(type & MEMBERSHIP_MESS == CAUSED_BY_LEAVE) && (type & REJECT_MESS == 0), then

in header:
hint = 0
sender = the group for which this is a notification (nul-terminated string)
num_groups = 0
groups is empty

message body is:
group_id	gid # ident of the group view (from arch.h)
int32		num_members = 1
char		vs_members[1][MAX_GROUP_NAME]