RFC 859 (rfc859) - Page 2 of 3
Telnet Status Option
Alternative Format: Original Text Document
RFC 859 May 1983
could lead to the nonterminating request loop problem discussed in
the General Consideration section of the TELNET Specification. This
option fits into the normal structure of TELNET options by deferring
the actual transfer of status information to the SB command.
5. Description of the Option
WILL and DO are used only to obtain and grant permission for future
discussion. The actual exchange of status information occurs within
option subcommands (IAC SB STATUS...).
Once the two hosts have exchanged a WILL and a DO, the sender of the
WILL STATUS is free to transmit status information, spontaneously or
in response to a request from the sender of the DO. At worst, this
may lead to transmitting the information twice. Only the sender of
the DO may send requests (IAC SB STATUS SEND IAC SE) and only the
sender of the WILL may transmit actual status information (within an
IAC SB STATUS IS ... IAC SE command).
IS has the subcommands WILL, DO and SB. They are used EXACTLY as used
during the actual negotiation of TELNET options, except that SB is
terminated with SE, rather than IAC SE. Transmission of SE, as a
regular data byte, is accomplished by doubling the byte (SE SE).
Options that are not explicitly described are assumed to be in their
default states. A single IAC SB STATUS IS ... IAC SE describes the
condition of ALL options.
Postel & Reynolds