Network Working Group R. Gellens
Request for Comments: 2066 Unisys
Category: Experimental January 1997
TELNET CHARSET Option
Status of this Memo
This memo defines an Experimental Protocol for the Internet
community. This memo does not specify an Internet standard of any
kind. Discussion and suggestions for improvement are requested.
Distribution of this memo is unlimited.
Abstract
This document specifies a mechanism for passing character set and
translation information between a TELNET client and server. Use of
this mechanism enables an application used by a TELNET user to send
and receive data in the correct character set.
Either side can (subject to option negotiation) at any time request
that a (new) character set be used.
1. Command Names and Codes
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 in
this document are reproduced here (excerpted from [1]):
All TELNET commands consist of at least a two byte sequence: the
"Interpret as Command" (IAC) escape character followed by the code
for the command. The commands dealing with option negotiation are
three byte sequences, the third byte being the code for the option
referenced. ... [O]nly the IAC need be doubled to be sent as data,
and the other 255 codes may be passed transparently. The
following are [some of] the defined TELNET commands. Note that
these codes and code sequences have the indicated meaning only
when immediately preceded by an IAC.
Gellens Experimental [Page 1]RFC 2066 TELNET CHARSET Option January 1997
NAME CODE MEANING
SE 240 End of subnegotiation parameters.
SB 250 Indicates that what follows is
subnegotiation of the indicated
option.
WILL 251 Indicates the desire to begin
performing, or confirmation that
you are now performing, the
indicated option.
WON'T 252 Indicates the refusal to perform,
or continue performing, the
indicated option.
DO 253 Indicates the request that the
other party perform, or
confirmation that you are expecting
the other party to perform, the
indicated option.
DON'T 254 Indicates the demand that the other
party stop performing, or
confirmation that you are no longer
expecting the other party to
perform, the indicated option.
IAC 255 Data Byte 255.
2. Command Meanings
A very simple meta-syntax is used, where most tokens represent
previously defined items (such as IAC); angle-brackets ("<>") are
used for items to be further defined; curly-braces ("{}") are used
around optional items; ellipses represent repeated sequences of
items; and quotes are used for literal strings.
IAC WILL CHARSET
The sender REQUESTS permission to, or AGREES to, use
CHARSET option subnegotiation to choose a character set.
IAC WON'T CHARSET
The sender REFUSES to use CHARSET option subnegotiation
to choose a character set.
Gellens Experimental [Page 2]RFC 2066 TELNET CHARSET Option January 1997
IAC DO CHARSET
The sender REQUESTS that, or AGREES to have, the other
side use CHARSET option subnegotiation to choose a
character set.
IAC DON'T CHARSET
The sender DEMANDS that the other side not use the
CHARSET option subnegotiation.
IAC SB CHARSET REQUEST { "[TTABLE ]" <Version> } <char set
list> IAC SE
Char set list:
<sep> <character set> { ... <sep> <character set> }
This message initiates a new CHARSET subnegotiation. It can only be
sent by a side that has received a DO CHARSET message and sent a WILL
CHARSET message (in either order).
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