rfc732.txt

RFC 相关的技术文档

    character position of the cursor. The xth through M-2nd characters
    on the line are shifted one character positon to the right. The new
    character is inserted at the vacated xth position. The M-1st
    character is lost. The position of the cursor remains unchanged.

    IAC SB DET CHAR DELETE IAC SE                    subcommand code: 16

    This subcommand deletes the character on the screen at the x-th
    position. The x-th character is removed and the characters x+1
    through M-1 are shifted one character position to the left to become
    the x-th through M-2nd characters. The M-1st character position is
    left empty. (For most terminals it will be set to a NUL or space.)
    The cursor position remains unchanged.

    IAC SB DET READ CURSOR IAC SE                    subcommand code: 17

    This subcommand requests the receiver to send the present position
    of the cursor to the sender.

    IAC SB DET CURSOR POSITION <x><y> IAC SE         subcommand code: 18

    where <x> and <y> are positive 8-bit binary integers.






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Data Entry Terminal Option



    This subcommand is sent by a Telnet implementation in response to a
    READ CURSOR subcommand to convey the coordinates of the cursor to
    the other side. Note: x is less than M and y is less than N.

    IAC SB DET REVERSE TAB IAC SE                    subcommand code: 19

    This subcommand causes the cursor to move to the previous tab
    position. If none exists on the present line, the cursor moves to
    the previous line and so on until a tab is found or the address
    (0,0) is encountered. When field protection is in effect the cursor
    moves to the beginning of the preceding unprotected field.

  Transmit Functions (For detailed semantics see Section 5.)

    IAC SB DET TRANSMIT SCREEN IAC SE                subcommand code: 20

    This subcommand causes the terminal to transmit all characters on
    the screen from position (0,0) to (M-1,N-1). The cursor will be at
    (0,0) after the operation is complete.

    IAC SB DET TRANSMIT UNPROTECTED IAC SE           subcommand code: 21

    This subcommand causes the terminal to transmit all characters in
    unprotected fields from position (0,0) to (M-1,N-1). The unprotected
    fields are separated by the field separator subcommand. The cursor
    will be at (0,0) or at the beginning of the first unprotected field
    after the operation is complete.

    IAC SB DET TRANSMIT LINE IAC SE                  subcommand code: 22

    This subcommand causes the terminal to transmit all data on the yth
    line where y is determined by the present position of the cursor.
    Data is sent from character position (0,y) to the end-of-line or
    position (M-1,y) whichever comes first. The cursor position after
    the transmission is one character position after the end of line
    condition or the beginning of the next line, (0,y+1).

    IAC SB DET TRANSMIT FIELD IAC SE                 subcommand code: 23

    This subcommand causes the terminal to transmit all data in the
    field presently occupied by the cursor. The cursor position after
    the operation is complete is one character position after the end of
    the field or, if that

    position is protected, at the beginning of the next unprotected
    field.






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Data Entry Terminal Option



    IAC SB DET TRANSMIT REST OF SCREEN IAC SE        subcommand code: 24

    This subcommand causes the terminal to transmit all characters on
    the screen from position (x,y) to (M-1,N-1) or until the end of
    text. (x,y) is the current cursor position. The cursor position
    after the operation is one character position after the last text
    character, or (0,0) if the last filled character position is
    (M-1,N-1).

    IAC SB DET TRANSMIT REST OF LINE IAC SE          subcommand code: 25

    This subcommand causes the terminal to transmit all characters on
    the yth line from position (x,y) to the end of line or (M-1,y)
    whichever comes first. (x,y) is the current cursor position. The
    cursor position after the operation is one character position after
    the last character of the line or the first character of the next
    line.

    IAC SB DET TRANSMIT REST OF FIELD IAC SE         subcommand code: 26

    This subcommand causes the receiver to transmit the rest of the
    characters in the field currently occupied by the cursor. The cursor
    position after the operation is at the beginning of the next field.

    IAC SB DET TRANSMIT MODIFIED IAC SE              subcommand code: 27

    This subcommand causes the receiver to transmit only those fields
    which have the modified attribute set. The cursor position after the
    operation is unchanged.

    IAC SB DET DATA TRANSMIT <x><y> IAC SE           subcommand code: 28

    This subcommand is used to preface data sent from the terminal in
    response to a user action or a TRANSMIT command. The parameters <x>
    and <y> indicate the initial position of the cursor. See the
    Transmit Subcommands subsection in Section 5 for more details. A
    DATA TRANSMIT subcommand may precede an entire transmission with
    each field being delineated by the FIELD SEPARATOR subcommand as
    would be the case in a response toa

    TRANSMIT UNPROTECTED. Or, it may precede each field as would be the
    case in a response to a TRANSMIT MODIFIED.

  Erase Functions

    IAC SB DET ERASE SCREEN IAC SE                   subcommand code: 29






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Data Entry Terminal Option



    This subcommand causes all characters to be removed from the screen.
    All fields regardless of their attributes are deleted. The cursor
    position after the operation will be (0,0). Most terminals set the
    erased characters to either NUL or space characters.

    IAC SB DET ERASE LINE IAC SE                     subcommand code: 30

    This subcommand causes all characters on the yth line to be removed
    from the screen, where y is the line of the current cursor position.
    All fields regardless of their attributes are deleted. The cursor
    position after this operation will be (0,y). Note: This operation
    can be easily simulated by the sequence: LINE DELETE, LINE INSERT.
    However, the order is important to insure that no data is lost off
    the bottom of the screen.

    IAC SB DET ERASE FIELD IAC SE                    subcommand code: 31

    This subcommand causes all characters in the field occupied by the
    cursor to be removed. The cursor position after the operation is at
    the beginning of the field.

    IAC SB DET ERASE REST OF SCREEN IAC SE           subcommand code: 32

    This subcommand causes all characters from position (x,y) to
    (M-1,N-1) to be removed from the screen. All fields regardless of
    their attributes are deleted. The cursor position after the
    operation is unchanged. This is equivalent to doing an ERASE REST OF
    LINE plus a LINE DELETE for lines greater than y.

    IAC SB DET ERASE REST OF LINE IAC SE             subcommand code: 33

    This subcommand causes all characters from position (x,y) to (M-1,y)
    to be removed from the screen All fields regardless of their
    attributes are deleted. The cursor position after the operation is
    unchanged.

    IAC SB DET ERASE REST OF FIELD IAC SE            subcommand code: 34

    This subcommand causes all characters from position (x,y) to the end
    of the current field to be removed from the screen. The cursor
    position after the operation is unchanged.

    IAC SB DET ERASE UNPROTECTED IAC SE              subcommand code: 35

    This subcommand causes all characters on the screen in unprotected
    fields to be removed from the screen. The cursor position after the






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Data Entry Terminal Option



    operation is at (0,0) or, if that position is protected, at the
    beginning of the first unprotected field.

  Format Functions

    IAC SB DET FORMAT DATA <format map><count> IAC SE
                                                     subcommand code: 36

    where <format map> is a two byte field containing the following
    flags:

      Byte 0
        Blinking                                 7
        Reverse Video                            6
        Right Justification                      5
        Protection                              3-4
        Intensity                               0-2
      Byte 1
        Modified                                1
        Pen Selectable                          0

    where:

    If the Blinking bit is set, the following field of <count>
    characters should have the Blinking attribute applied to it by the
    receiver.

    If the Reverse Video bit is set, the following field of <count>
    characters should be displayed by the receiver with video reversed.

    If the Right Justification bit is set, the input entered into the
    field of <count> characters should be right justified.

    The Protection field is two bits wide and may take on the

    following values:

      0         no protection
      1         protected
      2         alphabetic only
      3         numeric only

    The protection attribute specifies that the other side may modify
    any character (no protection), modify no characters (protected),
    enter only alphabetical characters (A-Z, and a-z) (alphabetic only),
    or enter only numerical characters (0-9,+,.,and -) (numeric only) in
    the following field of <count> bytes.





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Data Entry Terminal Option



    The Intensity field is 3 bits wide and should be interpreted in the
    following way:

      The values 0-6 should be used as an indication of the relative
      brightness to be used when displaying the characters in or entered
      into the following field <count> characters wide. The number of
      levels of brightness available should have been obtained
      previously by the Format Facility subcommand. The exact algorithm
      for mapping these values to the available levels of intensity is
      left to the implementors. A value of 7 in the intensity field
      indicates that the brightness should be off, and any characters in
      or entered into the field should not be displayed.

    If the Modified bit is set, the field is considered to have been
    modified and will be transmitted in response to a TRANSMIT MODIFIED
    subcommand.

    If the Pen Selectable bit is set, the field can be selected with the
    light pen. Note: Use of the light pen should be the subject of
    another Telnet option.

    <count> is 2 bytes that should be interpreted as a positive 16-bit
    binary integer representing the number of characters following this
    command which are affected by it.

    Data sent to the terminal or the Using Host for unwritten areas of
    the screen not in the scope of the count should be displayed with
    the default values of the format map. The default values are No
    Blinking, Normal Video, No Justification, No Protection and Normal
    Intensity. For example, suppose a FORMAT DATA subcommand was sent to
    the terminal with attributes Blinking and Protected and a

    count of 5 followed by the string "Name: John Doe". The string
    "Name:" would be protected and blinking, but the string "John Doe"
    would not be.

    This subcommand is used to format data to be displayed on the screen
    of the terminal. The <format map> describes the attributes that the
    field <count> bytes wide should have. This field is to start at the
    position of the cursor when the command is acted upon. The next
    <count> displayable characters in the data stream are used to fill
    the field. Subsequent REPEAT subcommands may be used to specify the
    contents of this field. If the sender specifies attributes that have
    not been agreed upon by the use of the Format Facility subcommand,
    the Telnet process should send an Error Subcommand to the sender,
    but format the screen as if the bit had not been set.






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Data Entry Terminal Option



    IAC SB DET REPEAT <count><char> IAC SE           subcommand code: 37

    where <count> is a positive 8-bit binary integer. <char> is an 8-bit
    byte containing an ASCII character.

    This subcommand is used to perform data compression on data being
    transferred to the terminal by encoding strings of identical
    characters as the character and a count. The repeated characters may
    be part of a field specified

    IAC SB DET SUPPRESS PROTECTION <negotiation> IAC SE
                                                     subcommand code: 38

    where <negotiation> may have the values of the Telnet option
    negotiation:

      251                 WILL
      252                 WONT
      253                 DO
      254                 DONT

    This subcommand is used to suppress the field protection in a
    non-destructive manner. Many data entry terminals provide the means
    by which protection may be turned on and off without modifying the
    contents of the screen or the terminal's memory. Thus, the
    protection may be turned off and back on without retransmitting the
    form.

    The default setting of the option is that protection is on, in other
    words

      IAC SB DET SUPPRESS PROTECTION WONT IAC SE
      IAC SB DET SUPPRESS PROTECTION DONT IAC SE

    Negotiation of this subcommand follows the same rules as
    negotiations of the Telnet options.

    IAC SB DET FIELD SEPARATOR IAC SE                subcommand code: 39

    It is necessary when transmitting only the unprotected portion of
    the screen to provide a means for delimiting the fields. Existing
    DET's use a variety of ASCII characters such as Tab, Group
    Separator, Unit Separator, etc. In order to maintain transparency of
    the NVDET this subcommand is used to separate the fields. Clearly,
    this incurs rather high overhead. This overhead can be avoided by
    using the Byte Macro Option (see Appendix 3).






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Data Entry Terminal Option



  Miscellaneous Commands

    IAC SB DET FN <code> IAC SE                      subcommand code: 40

    where: <code> is one byte.

    Many data-entry terminals provide a set of "function" keys which
    when pressed send a one-character command to the server. This
    subcommand describes such a facility. The values of the <code> field
    are defined by the user and server. The option merely provides the
    means to transfer the information.

    IAC SB DET ERROR <cmd> <error code> IAC SE       subcommand code: 41

    where:

      <cmd> is a byte containing the subcommand code of the subcommand
      in error.

      <error code> is a byte containing an error code.

      (For a list of the defined error codes see Appendix 2.)

    This subcommand is provided to allow DET option implementations to
    report errors they detect to the corresponding Telnet process. At
    this point it is worth reiterating that the philosophy of this
    option is that when an error is detected it should be reported;
    however, the implementation should attempt its best effort to carry
    out the intent of the subcommand or data in error.























John Day                                                       [page 15]