COLLABSRV(8) COLLABSRV(8)
NAME
collabsrv - multi-user collaboration
SYNOPSIS
collabsrv/collabsrv [ -f keyfile ] [ -n netaddress ] [ dir ]
collabsrv/servers/chatsrv
collabsrv/servers/mpx
collabsrv/servers/wbsrv
DESCRIPTION
Collabsrv listens on network address netaddress (default:
tcp!*!9999) for incoming requests to attach to services it
offers. The services are defined by the contents of direc-
tory dir (default: /services/collab). Collabsrv serves an
authenticated Styx connection that exports the contents of
dir/export (default: /services/collab/export). The exported
name space can contain directories from a shared file
server, but it will also contain a directory services giving
access to any collaborative activity services that have been
configured.
The services directory contains a single ctl file and a set
of subdirectories, numbered 0, 1 and so on. The ctl is used
to activate and access services. Each service instance is
identified by a name; clients connect to a given instance by
presenting its name. Each directory represents one instance
of a service. Each service instance corresponds to a name
space; the clients all share that name space. The name
space is determined by the service.
A client wishing to make use of the services must first
sys-dial(2) to connect to collabsrv, and authenticate and
mount the resulting Styx connection. It can do so using the
mount command (see bind(1)), or by using security-auth(2)
and Sys->mount (see sys-bind(2)). Normally, this is done by
collab(1).
A new connection to a particular service is requested by
opening the ctl file for reading and writing, writing a ser-
vice request to it, and reading back the number of the
directory corresponding to the requested service. A service
request written to ctl is text of the following form:
service id
where service is a string specifying the type of service
(eg, chat) and id is a string identifying the instance. The
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COLLABSRV(8) COLLABSRV(8)
server does not interpret id; it is up to the clients to
agree a naming convention (often using the name of a shared
file as an id). Collabsrv will connect to instance id of the
requested service type if one is already running, or start
one if necessary; the write request returns an error if the
service cannot be started. Following a successful write to
ctl, a read will return the number of the service directory
containing the client's private connection to that service
instance. Closing the ctl file disconnects from the ser-
vice.
Available services are defined by a configuration file
/services/collab/services.cfg, which contains a sequence of
configuration entries of the following form:
service
path=disfile
where service is the name presented in a service request,
and disfile names a Dis file implementing that service; path
names are interpreted relative to /services/collab, but usu-
ally refer to files in /dis/collabsrv/servers.
Each collabsrv service is represented by a name space pecu-
liar to that service. The interface to the service is
therefore implemented by a service-specific Styx server
(disfile in the configuration file). Current services are
described below.
Chat
Chatsrv provides a simple service for the exchange of text
messages. It serves a name space containing two files. The
files together represent a single messaging group:
users A read-only file that lists the user names of the
current members of the group, one per line. The ver-
sion number of the file's Qid (see sys-stat(2)) is
incremented each time a client arrives or leaves.
msgs
A client connects to the messaging group by opening
this file. A message is sent to the group by writing
to the file. Each read returns the next unread mes-
sage, prefixed by the name of the sender, or <you>
for a message sent by the current client. A client
sees no messages sent before it connects. Messages
are delivered in the same order to all clients;
clients receive their own messages. Two special mes-
sages are generated by the server:
+++ name has arrived
--- name has left
as clients come and go.
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Multiplexor
Mpx offers a general fan-out/fan-in multiplexing service for
a tree of processes, with one controlling or root process at
the root of the tree, and a set of client processes at the
leaves of the tree. It serves three files:
root An exclusive-use file read and written by the root
process to communicate with the leaf processes.
leaf Client processes read and write this file to communi-
cate with the root process (each open of leaf is
independent). It cannot be opened until a process
has opened root. After root has been closed, and any
remaining messages on leaf have been read, subsequent
reads will return zero bytes (end-of-file).
users A read-only text file that lists the user names of
processes that currently have leaf open. There is
one line per leaf, containing a unique numeric ID for
the leaf, a space, and then the users's name.
A message written to root is replicated on all instances of
leaf that are currently open. A message written to any
instance of leaf will be read by the process reading root.
Data written to both root and leaf has a prefix added to
identify the sender, causing messages to have the following
format:
seq clientid op name data
where seq is a unique message sequence number; clientid is a
unique number identifying the process amongst currently con-
nected clients, with 0 identifying the root process; op is a
single character giving the message type (see below); name
is the sending process's user name; and data is the data
written by the process, which can be text or binary (the
message header is always text). Mpx also generates messages
as root and leaf processes arrive and leave. These are
identified by op. The various op values and the direction in
which they can occur are listed below:
a New leaf process has arrived (leaf to root)
M Message from root process (root to leaf)
m Message from leaf process (leaf to root)
L Root process has left (root to leaf)
l Leaf process has left (leaf to root)
Messages are only ever sent from the root to all leaves, or
from a leaf to the root, never from leaf to leaf; the root
process could of course rebroadcast a message from a leaf.
The multiplexor service is used to implement a real-time
poll (see poll and poller in collab-clients(1)), but could
be used for several other services, such as auctions.
Whiteboard
Wbsrv offers a service for sharing a simple line drawing.
It serves two files:
wb.bit
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COLLABSRV(8) COLLABSRV(8)
A read-only file containing an uncompressed image(6)
with the current state of the drawing.
strokes
This file is read and written to exchange strokes with
other clients. A stroke has the following representa-
tion:
colour width x0 y0 x1 y1 ...
where all values are space-separated decimal numbers:
colour is an index into the rgbv(6) colour map; width
is the width of the line in pixels, and the sequence of
coordinate pairs defines the connected line segments to
draw. A stroke is transmitted from one client to all
others by writing a stroke description to the file in a
single write. Each read returns a description of a
stroke made by another client.
A whiteboard client should read the wb.bit file to obtain
its image, then read the strokes file for instructions to
keep it up to date.
FILES
/services/collab/export/services active service directory
/services/collab/services.cfg maps service names to mod-
ules
/dis/collabsrv/servers service implementation
modules
SOURCE
/appl/collabsrv
/appl/collabsrv/servers
/appl/collabsrv/lib
SEE ALSO
collab(1), collab-clients(1)
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