tels(7)tels(7)NAME
tels, telm - STREAMS Telnet slave (pseudo-terminal) driver, STREAMS
Telnet master driver (used by telnetd only), respectively
SYNOPSISDESCRIPTION
A Telnet pseudo-terminal consists of a tightly-coupled pair of charac‐
ter devices, called the master device and slave device. The master and
slave device drivers work together to provide a Telnet connection on
the server side where the master provides a connection to and the slave
provides a terminal device special file access for the Telnet applica‐
tion processes, as depicted below:
--------------------------
| Pseudo terminal functions|
Application <--> |--------------------------| <--> telnetd
Processes | Slave | Master |
| (tels) | (telm) |
--------------------------
The slave driver, with (STREAMS pty emulation module) and (STREAMS line
discipline module) pushed on top (not shown for simplicity), provides a
terminal interface as described in termio(7). Whereas devices that
provide the terminal interface described in termio(7) have a hardware
device behind them; in contrast, the slave device has manipulating it
through the master side of the Telnet pseudo terminal.
There are no nodes in the file system for each individual master
device. Rather, the master driver is set up as a STREAMS clone(7)
driver with its major device number set to the major for the clone
driver and its minor device number set to the major for the driver.
The master driver is opened by telnetd using the open(2) system call
with as the device file parameter. The clone open finds the next
available minor number for the master device. The master device is
available only if it and its corresponding slave device are not already
opened.
In order to use the STREAMS Telnet subsystem, a node for the master
driver and N number of Telnet slave devices must be installed.
The number of slave devices is set by a kernel tunable parameter called
This can be modified using SAM; its default and minimum value is 60.
The value of is the upper limit of the number of telnet sessions that
can be opened.
Multiple opens are allowed on the Telnet slave device.
The master and slave drivers pass all STREAMS messages to their adja‐
cent drivers. When the connection is closed from the Telnet client
side, an message is sent to the corresponding slave device which will
render that slave device unusable. The process on the slave side gets
the errno when attempting a write(2) system call to the slave device
file but it will be able to read any data remaining in the slave
stream. Finally, when all the data has been read, the read(2) system
call will return 0, indicating that the slave can no longer be used.
AUTHOR
and were developed by HP.
FILES
Streams Telnet master clone device
Streams slave devices where
N is the minor number of the slave device and 0 < N
<
SEE ALSOinsf(1M), open(2), ioctl(2), streamio(7), ldterm(7), telnetd(1M),
ptem(7).
tels(7)