connection setup
----------------
entirely string based (for backwards compatiblity)

1.Host A opens TCP connection to host B

2.Host B responds with header specifying server name and protocol version (human readable), example:
OpenSim 0.1-r503, running OGS protocol 1.0

3.Host B responds with machine-readable PROTO message:
PROTO 1 0
syntax is PROTO <majorversion> <minorversion>

4.Host A sends PROTO message
PROTO 1 0

5.If both hosts match, authentication mechanism is negotiated:
AUTH statickeys ssl
syntax is AUTH <authentication methods supported>
methods can be:
authkeys - must be implemented to be compliant, standard send/receive static keys
ssl - causes the binary exchange to take place over a new encrypted (via SSL) channel), need to discuss how to implement this properly (need certificates with the grid server as root authority).
The most secure one (as configured by preference list) is chosen and the response sent:
AUTHOK statickeys
syntax is AUTH <chosen authentication method>
If none are allowed, AUTHBAD is sent:
NOAUTH statickeys I don't support that method
syntax is:
NOAUTH <method>

If the protocols do not match, the host with the newer protocol will evaluate if it is backwards compatible enough. If not, the FAIL response is sent:
FAIL PROTO you are running too old a protocol, please update
syntax is:
FAIL <command> <message>

FAIL may also be sent at any other point for any command

6.Authentication with statickeys takes place, or whatever other method
Host A sends:
AUTHKEY blabla
Host B responds:
AUTHKEY blabla

both hosts check the keys against their receive_key config and send the appropiate response:
READY
or
FAIL AUTHKEY sorry, that key is wrong
CLOSE

guess what CLOSE does ;)

7.Once a READY is received by host A, host A sends a READY to host B

8.Once both ends have sent a READY, we go from text mode into binary mode and can exchange messages as below. Though rare, a host may also send FAIL READY, thus closing the connection.

note, PROTOXML may be used in place of PROTO above and will cause the XML-serialised form of all these messages to be sent.

messages
--------

header (prepended to all messages)
	uint8  protocol_version_major
	uint8  protocol_version_minor
	uint16 message_type
	uint32 message_size
	byte flags (right to left)
		final message (close connection after this)
		request ack (sent with an empty message_size and message_type=0 to act as a ping)
		reserved
		reserved
		reserved
		reserved
		reserved
		reserved

each of the messages below will be assigned a type based on an enum or some such:

user control
	UUID AgentID
	UUID SessionID
	UUID SecureSessionID
	double startpos_x
	double startpos_y
	int8 firstname_length
	char[x] firstname
	int8 lastname_length
	char[x] lastname
	byte flags (right to left)
		create/update child agent
		upgrade child agent to adult
		downgrade adult agent to child
		destroy agent
		reserved
		reserved
		reserved
		reserved

neighbour control
	UUID   NeighbourID
	uint16 sendkey_length
	char[x] sendkey
	uint16 recvkey_length
	char[x] recvkey
	uint32 regionlocX
	uint32 regionlocy
	uint32 sim_ip
	uint16 sim_port
	byte flags (right to left)
		create/update neighbour
		delete neighbour
		reserved
		reserved
		reserved
		reserved
		reserved
		reserved