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BSD 2.11 - man page for bk (bsd section 4)

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BK(4)											    BK(4)

NAME
       bk - line discipline for machine-machine communication (obsolete)

SYNOPSIS
       Not currently supported under 2.11BSD

DESCRIPTION
       This  line  discipline provides a replacement for the old and new tty drivers described in
       tty(4) when high speed output to and especially input from another machine is to be trans-
       mitted  over  a	asynchronous communications line.  The discipline was designed for use by
       the Berkeley network.  It may be suitable for uploading of data from microprocessors  into
       the  system.  If you are going to send data over asynchronous communications lines at high
       speed into the system, you must use this discipline, as the system  otherwise  may  detect
       high input data rates on terminal lines and disables the lines; in any case the processing
       of such data when normal terminal mechanisms are involved saturates the system.

       The line discipline is enabled by a sequence:

	    #include <sgtty.h>
	    int ldisc = NETLDISC, fildes; ...
	    ioctl(fildes, TIOCSETD, &ldisc);

       A typical application program then reads a sequence  of	lines  from  the  terminal  port,
       checking  header and sequencing information on each line and acknowledging receipt of each
       line to the sender, who then transmits another line of data.   Typically  several  hundred
       bytes  of  data and a smaller amount of control information will be received on each hand-
       shake.

       The old standard teletype discipline can be restored by doing:

	    ldisc = OTTYDISC;
	    ioctl(fildes, TIOCSETD, &ldisc);

       While in networked mode, normal teletype output functions take place.  Thus, if an  8  bit
       output data path is desired, it is necessary to prepare the output line by putting it into
       RAW mode using ioctl(2).  This must be done before changing the discipline with	TIOCSETD,
       as most ioctl(2) calls are disabled while in network line-discipline mode.

       When  in network mode, input processing is very limited to reduce overhead.  Currently the
       input path is only 7 bits wide, with newline the only recognized character, terminating an
       input  record.	Each  input record must be read and acknowledged before the next input is
       read as the system refuses to accept any new data when there is a record  in  the  buffer.
       The  buffer is limited in length, but the system guarantees to always be willing to accept
       input resulting in 512 data characters and then the terminating newline.

       User level programs should provide sequencing and checksums on the information to  guaran-
       tee accurate data transfer.

SEE ALSO
       tty(4)

DIAGNOSTICS
       None.

BUGS
       The  Purdue  uploading line discipline, which provides 8 bits and uses timeout's to termi-
       nate uploading should be incorporated into the standard system, as it is much  more  suit-
       able for microprocessor connections.

4th Berkeley Distribution		 January 27, 1996				    BK(4)
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