This is a protocol which I (Vasya Novikov) think would be best for the game Points.

1) The communication is done via small simple text messages -- in both directions. (From server to the client and vice versa.)

2) Protocol messages are numbered -- one enumeration for the server and one for the client.

The main protocol structure:

req N; 		-- request all server messages starting at N.
req N1-N2; 	-- request server messages from N1 to N2.
null N; 	-- there are no messages that must be sent. The last message number was N.
msg N .....; 	-- I'm sending some message and it has number N.

Structure-messages "req", "null" aren't stored and numbered. Structure-message "msg" should be.
If the client wants to update himself, he sends the "req N" request.

From now I'm forgetting about all these structure-messages and focus on what comes after the "msg N". I'll call them just messages.
The form of the messages is:
Command <arguments>

Basic Client->Server messages:

subscribe <room>		- the user is "entering" the room and get's subscribed to updates. "room" is a string that represents a room.
unsubscribe <room>		- unsubscribing
chat <room> <message>		- send chat
kick <room>			- kick someone from a room.
version <text>			- the client's version. If it is not up-to-date - the server should block the user.
getGameRooms <room>		- get games played inside a global (language) room.
getRoomList			- return all global (language) rooms

makeMove <room> <move>		- make a move. The move is in the form B[15:4], like in SGF.
requestUndo <room>		- request an undo
agreeUndo			- argee for an undo for your opponent.
addTime <room>			- add time to your opponent
gameSTOP <room>			- the game action "STOP"
gamePass <room>			- the game action "pass"
gameSettings <room> <settings>	- game settings in the form like in  SGF
gameInit <room>			- initializes the game.. Starts the timers and generates crosses.
privGameChat <room> <message>	- sends a chat to your opponent if you're the player or to all other spectators if you're a spectator

register <nick> <text>		- here must be some registration info. Maybe OpenID, maybe pass+email...
login <nick> <text>		- log in.
userInfo <text>			- userinfo
.....
....

Basic Server-Client messages:

subscribed <room>
unsubscribed <room>
chat <room>
kicked <room>

moveMaked <room> <move> <time>		(time left)
undoMaked <room>
requestingUndo <room>
addedTime <room>
.....
....


Any suggestions and criticism is welcome.