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Annotation of researchv10dc/man/manb/bk.4, revision 1.1

1.1     ! root        1: .TH BK 4
        !             2: .UC 4
        !             3: .SH NAME
        !             4: bk \- line discipline for machine-machine communication
        !             5: .SH SYNOPSIS
        !             6: .B #include <sgtty.h>
        !             7: .PP
        !             8: .B int ldisc = NETLDISC, fildes;
        !             9: \&...
        !            10: .PP
        !            11: .B ioctl(fildes, TIOCSETD, &ldisc);
        !            12: .SH DESCRIPTION
        !            13: This line discipline provides a replacement for the old and new
        !            14: tty drivers described in
        !            15: .IR tty (4)
        !            16: when high speed output to
        !            17: and especially input from another machine is to be transmitted
        !            18: over a asynchronous communications line.  The discipline
        !            19: was designed for use by the Berkeley network
        !            20: .IR net (1)
        !            21: but is
        !            22: well suited to uploading of data from microprocessors into
        !            23: the system.  If you are going to send data over asynchronous
        !            24: communications lines at high speed into the system, you must
        !            25: use this discipline, as the system otherwise may detect high
        !            26: input data rates on terminal lines and disables the lines;
        !            27: in any case the processing of such data when normal terminal
        !            28: mechanisms are involved saturates the system.
        !            29: .PP
        !            30: A typical application program then reads a sequence of lines from
        !            31: the terminal port, checking header and sequencing information on each
        !            32: line and acknowledging receipt of each line to the sender, who then
        !            33: transmits another line of data.  Typically several hundred bytes of
        !            34: data and a smaller amount of control information will be received on
        !            35: each handshake.
        !            36: .PP
        !            37: The old standard teletype discipline can be restored by doing:
        !            38: .sp
        !            39: .ft B
        !            40: ldisc = OTTYDISC;
        !            41: 
        !            42: ioctl(fildes, TIOCSETD, &ldisc);
        !            43: .ft R
        !            44: .sp
        !            45: While in networked mode, normal teletype output functions take place.
        !            46: Thus, if an 8 bit output data path is desired, it is necessary
        !            47: to prepare the output line by putting it into RAW mode using
        !            48: .IR ioctl (2).
        !            49: This must be done
        !            50: .B before
        !            51: changing the discipline with TIOCSETD, as most
        !            52: .IR ioctl (2)
        !            53: calls are disabled while in network line-discipline mode.
        !            54: .PP
        !            55: When in network mode, input processing is very limited to reduce overhead.
        !            56: Currently the input path is only 7 bits wide, with newline the only
        !            57: recognized character, terminating an input record.
        !            58: Each input record must be read and acknowledged before the next input
        !            59: is read as the system refuses to accept any new data when there
        !            60: is a record in the buffer.  The buffer is limited in length, but the
        !            61: system guarantees to always be willing to accept input resulting in
        !            62: 512 data characters and then the terminating newline.
        !            63: .PP
        !            64: User level programs should provide sequencing and checksums on the
        !            65: information to guarantee accurate data transfer.
        !            66: .SH "SEE ALSO"
        !            67: tty(4)
        !            68: .SH BUGS
        !            69: A standard program and protocol should be defined for
        !            70: uploading data from microprocessors, so that havoc doesn't
        !            71: result.
        !            72: .PP
        !            73: A full 8-bit input path should be provided with a mechanism
        !            74: for escaping newlines into an input packet.

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