CVE Network Protocol

CVE Network Protocol: Working Draft

The protocol must support a rich set of chat capabilities: chat in room, chat in interest groups, chat with everyone... Chat is appropriate for a TCP-based protocol.
The protocol must support a rich set of interactions with the virtual environment. Eventually these will include avatar motion and actions, manipulation of whiteboard/chalkboard, etc. Those interactions which are transient (e.g. avatar motion) are appropriate for UDP, while those that are persistent (e.g. writing on a whiteboard) are appropriate for TCP.
The protocol must support a rich set of interactions with computer science educational applications, such as text editors and compilers. These tools will be integrated into the environment; we do not have to work with existing tools unmodified.
The protocol must be somewhat concise. Later versions may include compression on large packets.
The protocol must be somewhat secure. Later versions may include encryption. More likely, we will use ssh tunnels.

Where to Start

Start with TCP-only connections. When we add UDP, the messages will be identical, just on a different channel.
Each normal, individual message is self-contained, human readable, on a single line.
So far everything is going through a single server. We may add peer/peer capabilities down the road, especially for e.g. audio/video direct connections.

Examples

These examples are intended to give you the flavor of what we are doing. This list is not complete nor is it written in stone. Some of these items are really local client commands, not network protocol commands. For each command we need to ask: does it need to go the server? and then: which client(s) should the server forward it on to? and then: does it require a reply, and if so, from whom? Lastly: for each command, does it require that the server remember the state change and store it in a database?

Every command can be abbreviated by a unique prefix. Common commands can be abbreviated with nonunique prefixes. Each client avatar has a current default command which executes for lines not beginning with \.

Chatting

Example	Description
\say hello	chats to the current room
\tell joe hello	chats to a specific person
\tell groupname hello	chats to a specific group
\tell sessionname hello	chats to a specific session
\group hello	chats to the current group
\sig hello	chats to the current special interest group
\course hello	chats to the current course
\emote	a supposedly non-verbal

Establishing groups

There are groups (temporary membership, current-session oriented), sigs (persistent membership), and courses (persistent membership, extra structure and permissions)

Example	Description
\invite	invite (currently selected person) to join group
\disband	disband current group
\groups	list my groups
\lsgroups	list all groups
\makesig unicon	create a special interest group
\makecourse cs371	create a course
\sig=unicon	sets the current/default special interest group you are sending to
\unicon	sends a message to any sig by name
\join unicon	join (subscribe to listen) a sig
\course cs371	sets the current course you are sending to
\ignore joe	discard all messages from user joe

A discussion on 12/19/05 produced the following

Example	Description
\createsession sessiontype sessionname	create a (temporary) group
\createsession sessionname sessionid	server assigns id to created (temporary) group
\destroysession sessionname	destroy a (temporary) group
\subsession sessiontype sessionname	create a subgroup
\invite sessionname username(s)	client invites user(s) to join group
\invite sessiontype sessionname	server forwards invitation to user(s) to join group
\join sessionname	accept membership
\decline sessionname	decline membership
\leave sessionname	exit membership
\dismiss sessionname username	kick someone out
\listsessions	client requests
\listsessions ssnname, ssntype, ssnname, ssntype, ...	server responds
\listmembers sessionname
\requestcontrol sessionname
\releasecontrol sessionname
\givecontrol sessionname username

Avatar and environment manipulation

Example	Description
\move 0,0,3.5	move to (x,y,z)
\look	get a 2D detailed look at nearest 2D object
\look board	get a 2D detailed look at the nearest whiteboard
\look screen	get a 2D detailed look at the nearest PC screen
\look up	go back to 3D view
\look 0,0,3.5	(turn and) look at (x,y,z)
\move sh371	move (teleport) to sh371
\pen red	set the current pen to red
\whiteboard sh118b-a	set/lock the current whiteboard to sh118b-a
\draw 50,50	set (x,y) on the nearest board to current pen color
\drawline 50,50,55,30	draw line from (x,y)-(x2,y2) on the nearest board to current pen color
\fillrectangle 50,50,10,10 fill rectangle from (x,y) with (width,height) on the nearest board to current pen color
\erase	erase the nearest board
\door	toggle nearest door more open or closed
\hand	toggle (raise/lower) hand
\follow	follow the currently targeted user
\voice [on off]	enable disable realtime microphone
\sound [on off]	enable disable realtime speaker
\video [on off]	enable disable realtime videocamera feed

File Transfer

Example	Description
\putfile dat/avatars/curtis.avt 206	dat/avatars/curtis.avt is the file to upload, and it is 206 bytes. Immediately after the newline (after the 6) the actual contents of the file (ASCII or binary; use writes()/reads() for no newline-handling) would be sent.
\getfile dat/avatars/curtis.avt	this asks the server to execute a \putfile

Issues:

for large files, break reads/writes up into chunks and service other active connections while transfer is in progress. Under such a circumstance, connection/session manager has to remember for a given connection that it has a file transfer in-progress and new data is not a new command.
permissions model: do not allow this at chat command line!
private file transfer: \putfile userid dat/...

Miscellaneous

Example	Description
\quit!	exits immediately
\exit	exits with a grace period
\afk	marks you as away from keyboard
\who	show who is on the system
\loc	shows your current location
\log [on off]	turns on/off your private recorder
\cmd say	sets the default command to \say

Teacher/lecture tasks

Example	Description
\give joe pen	give joe permission to draw on the board
\give joe voice	give joe permission to speak
\give joe legs	give joe permission to move
\take joe ...	remove students' specific permissions
\stop joe	remove all of joe's permissions, he is paralyzed

Administrator tasks

Example	Description
\enroll joe cs371	adds joe to a class
\kill joe	dumps joe out of the application
\lock joe	prevents joe from logging in any more

Collaborative IDE and Browser Protocol

Issues:

two sources of changes need to be transmitted: changes from the textlist (or editabletextlist, or htmlbrowser) widget, and changes from the scrollbar. Except: scrollbar changes already propagate to the textlist widget, so perhaps we can catch them there.
commands messages vs. content messages
how often do commands synchronize?
who is keeping track of who-all is in the collaborative session
who is keeping track of who owns the write "token"
commands for requesting and releasing the write "token"
Refactoring of groups to support: chat, voice, and browsing/editing groups
Invitation-based session creation.