As per Relevance of the word indicated, we have this rfc below:
Network Working Group R.
Request for Comments: 2066
Category: Experimental January 1997
TELNET CHARSET
Status of this
This memo defines an Experimental Protocol for the
community. This memo does not specify an Internet standard of
kind. Discussion and suggestions for improvement are requested
Distribution of this memo is unlimited
This document specifies a mechanism for passing character set
translation information between a TELNET client and server. Use
this mechanism enables an application used by a TELNET user to
and receive data in the correct character set
Either side can (subject to option negotiation) at any time
that a (new) character set be used
1. Command Names and
CHARSET.......................42
REQUEST ....................01
ACCEPTED ...................02
REJECTED ...................03
TTABLE-IS ..................04
TTABLE-REJECTED ............05
TTABLE-ACK .................06
TTABLE-NAK .................07
As a convenience, standard TELNET text and codes for commands used
this document are reproduced here (excerpted from [1]):
All TELNET commands consist of at least a two byte sequence:
"Interpret as Command" (IAC) escape character followed by the
for the command. The commands dealing with option negotiation
three byte sequences, the third byte being the code for the
referenced. ... [O]nly the IAC need be doubled to be sent as data
and the other 255 codes may be passed transparently.
following are [some of] the defined TELNET commands. Note
these codes and code sequences have the indicated meaning
when immediately preceded by an IAC
Gellens Experimental [Page 1]
RFC 2066 TELNET CHARSET Option January 1997
NAME CODE
SE 240 End of subnegotiation parameters
SB 250 Indicates that what follows
subnegotiation of the
option
WILL 251 Indicates the desire to
performing, or confirmation
you are now performing,
indicated option
WON'T 252 Indicates the refusal to perform
or continue performing,
indicated option
DO 253 Indicates the request that
other party perform,
confirmation that you are
the other party to perform,
indicated option
DON'T 254 Indicates the demand that the
party stop performing,
confirmation that you are no
expecting the other party
perform, the indicated option
IAC 255 Data Byte 255.
2. Command
A very simple meta-syntax is used, where most tokens
previously defined items (such as IAC); angle-brackets ("<>")
used for items to be further defined; curly-braces ("{}") are
around optional items; ellipses represent repeated sequences
items; and quotes are used for literal strings
IAC WILL
The sender REQUESTS permission to, or AGREES to,
CHARSET option subnegotiation to choose a character set
IAC WON'T
The sender REFUSES to use CHARSET option
to choose a character set
Gellens Experimental [Page 2]
RFC 2066 TELNET CHARSET Option January 1997
IAC DO
The sender REQUESTS that, or AGREES to have, the
side use CHARSET option subnegotiation to choose
character set
IAC DON'T
The sender DEMANDS that the other side not use
CHARSET option subnegotiation
IAC SB CHARSET REQUEST { "[TTABLE ]" }
list> IAC
Char set list
<character set> { ... <character set> }
This message initiates a new CHARSET subnegotiation. It can only
sent by a side that has received a DO CHARSET message and sent a
CHARSET message (in either order).
The sender requests that all text sent to and by it be encoded in
of the specified character sets
If the string [TTABLE] appears, the sender is willing to accept
mapping (translation table) between any character set listed in <
set list> and any character set desired by the receiver
is an octet whose binary value is the highest
level of the TTABLE-IS message which can be sent in response.
field must not be zero. See the TTABLE-IS message for the
version values
is a sequence of 7-BIT ASCII printable characters
The first octet defines the separator character (which must
appear within any character set). It is terminated by the IAC
sequence. Case is not significant. It consists of one or
character sets. The character sets should appear in order
preference (most preferred first).
is a separator octet, the value of which is chosen by
sender. Examples include a space or a semicolon. Any value
than IAC is allowed. The obvious choice is a space or any
punctuation symbol which does not appear in any of the character
names
Gellens Experimental [Page 3]
RFC 2066 TELNET CHARSET Option January 1997
<Character set> is a sequence of 7-BIT ASCII printable characters
Case is not significant
If a requested character set name does not start with "X-" or "x-",
it MUST be registered with the Internet Assigned Number
(IANA) [2].
The receiver responds in one of four ways
If the receiver is already sending text to and expecting text
the sender to be encoded in one of the specified character sets,
sends a positive acknowledgment (CHARSET ACCEPTED); it MUST
ignore the message. (Although ignoring the message is
suggested by some interpretations of the relevant RFCs ([1], [3]),
the interests of determinacy it is not permitted. This ensures
the issuer does not need to time out and infer a response,
avoiding (because there is no response to a positive acknowledgment
the non-terminating subnegotiation which is the rationale in the
for the non-response behavior.)
If the receiver is capable of handling at least one of the
character sets, it can respond with a positive acknowledgment for
of the requested character sets. Normally, it should pick the
set it is capable of handling but may choose one based on its
preferences. After doing so, each side MUST encode subsequent
in the specified character set
If the string [TTABLE] is present, and the receiver prefers to use
character set not included in , and is capable
doing so, it can send a translate table (TTABLE-IS) response
If the receiver is not capable of handling any of the
character sets, it sends a negative acknowledgment (
REJECTED).
Because it is not valid to reply to a CHARSET REQUEST message
another CHARSET REQUEST message, if a CHARSET REQUEST message
received after sending one, it means that both sides have sent
simultaneously. In this case, the server side MUST issue a
acknowledgment. The client side MUST respond to the one from
server
IAC SB CHARSET ACCEPTED IAC
This is a positive acknowledgment response to a CHARSET
message; the receiver of the CHARSET REQUEST message
its receipt and accepts the indicated character set
Gellens Experimental [Page 4]
RFC 2066 TELNET CHARSET Option January 1997
is a character sequence identical to one of
character sets in the CHARSET REQUEST message. It is
by the IAC SE sequence
Text messages which follow this response must now be coded in
indicated character set. This message terminates the
CHARSET subnegotiation
IAC SB CHARSET REJECTED IAC
This is a negative acknowledgment response to a CHARSET
message; the receiver of the CHARSET REQUEST message
its receipt but refuses to use any of the requested
sets. Messages can not be sent in any of the indicated
sets. This message can also be sent by the sender of a TTABLE-
message, if multiple TTABLE-NAK messages were sent in response
This message terminates the current CHARSET subnegotiation
IAC SB CHARSET TTABLE-IS IAC
In response to a CHARSET REQUEST message in which [TTABLE]
specified, the receiver of the CHARSET REQUEST
acknowledges its receipt and is transmitting a pair of
which define the mapping between specified character sets
is an octet whose binary value is the version level
this TTABLE-IS message. Different versions have different syntax
The lowest version level is one (zero is not valid). The
highest version level is also one. This field is provided so
future versions of the TTABLE-SEND message can be specified,
example, to handle character sets for which there is no
one-to-one character-for-character translation. This
include some forms of multi-octet character sets for
translation algorithms or subsets need to be sent
Syntax for Version 1:
< char size 1> < char count 1> <
set name 2> 