PLAP(3)PLAP(3)NAMEplap - USR/3Com Edgeserver packet bus link access protocol
SYNOPSIS
bind -a '#X' /net
/net/plap/clone
/net/plap/n/ctl
/net/plap/n/data
/net/plap/n/local
/net/plap/n/remote
/net/plap/n/status
/net/plap/n/listen
DESCRIPTION
The plap driver serves a three-level directory giving access to the
link level protocol used by an Edgeserver card to communicate with
other cards in a USR/3Com chassis. On first attach (usually by a
bind(1) to /net) the driver opens a connection to the packet bus device
#Y described in pbus(3). It multiplexes that connection using a spe‐
cialised member of the LAP family of protocols.
The top level directory contains a single directory naming the proto‐
col, plap. It contains a clone file and a set of conversation directo‐
ries numbered from 0 to 127; only active conversation directories are
present.
Opening the clone file allocates a new conversation directory n. The
file descriptor will point to the control file, ctl, of that directory.
Reading the file returns a text string giving the conversation number.
Each conversation directory contains six files. The connection is con‐
trolled by writing text strings to the ctl file. Once a connection has
been established, data is exchanged with the remote peer by reading and
writing the data file.
A plap address has the form:
[ slot. ] chan!sap
where slot is a chassis slot number, chan is a logical channel (eg, a
modem number), and sap is a number representing a `service access
point'.
The following control messages are supported:
connect remoteaddr [ localaddr ]
Make a connection to the given remote address (of the form given
above). If a local address is not specified, the system will
assign an unused address dynamically (the local chassis slot
number is of course fixed). Connect fails if the connection is
already announced or connected, or localaddr is already in use.
announceaddress
Set the local address to address and accept incoming calls to
that address. If no address is specified, all incoming calls to
addresses not explicitly announced will be accepted by this con‐
nection. Announce fails if the connection is already announced
or connected, or the local address specified is already in use.
The remote and local files contain the remote and local addresses for
the connection in the full address form slot.chan!sap. The status file
returns a line giving the directory name, number of active opens, and
the state of the connection.
A process listens for incoming calls by opening the listen file using
sys-open(2). The open will block until a call arrives, when it will
return a file descriptor open on the ctl file of the newly accepted
connection, which can be read to find the directory number and thus the
other files.
The device follows the conventions that allow dial, announce and listen
of dial(2) to do the work needed to establish and manipulate network
connections.
SOURCE
/os/pc/devplap.c
SEE ALSOpbus(3)BUGS
The driver cannot be included in the public distribution.
PLAP(3)
