RFC651 - Revised Telnet status option

Revised Telnet Status OptionNIC 31154 (25 Oct. 74)Request for Comments: 651D. Crocker (UCLA-NMC) 25 Oct. 74RFC# 651Online file: <[ISI]<DCROCKER>STATUS-OPTION-REVISION.RNO                     Revised Telnet Status Option1. Command name and code   STATUS  52. Command meanings   As described in the NAOL and NAOP option specifications, this option applies   to a simplex connection.      IAC DO STATUS          Sender of DO wishes to be able to send requests for status-of-options          information, or confirms that he is willing to send such requests.      IAC WILL STATUS          Sender of WILL wishes or agrees to send status information,          spontaneously or in response to future requests.      IAC DON'T STATUS          Sender refuses to carry on any further discussion of the current          status of options.      IAC WON'T STATUS          Sender refuses to carry on any further discussion of the current          status of options.      IAC SB STATUS SEND IAC SE         Sender requests receiver to transmit his (the receiver's) perception          of the current status of Telnet options. The code for SEND is 1. (See          below.)      IAC SB STATUS IS ... IAC SE          Sender is stating his perception of the current status of Telnet          options. The code for IS is 0. (See below.)3. Default   DON'T STATUS/WON'T STATUS. That is, the current status of options will not    be discussed.4. Motivation for the option   This option allows a user/PRocess to verify the current status of Telnet    options (e.g., echoing) as viewed by the person/process on the other end of    the Telnet connection. Simply renegotiating options could lead to the    nonterminating request loop problem discussed in (NIC #16237). The changes    to the option, described in this paper, allow STATUS to fit into the normal    structure of Telnet options, by deferring the actual transfer of status    information to the SB command. Additionally, the numbers of bytes that must    be sent to describe the state of the options has been considerably reduced.5. Description of the option   WILL/DO are now 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.   The following is an example of use of the option:      Host1: IAC DO STATUS      Host2: IAC WILL STATUS         (Host2 is now free to send status information at any time.          Solicitations from Host1 are NOT necessary. This should not produce          any dangerous race conditions. At worst, two IS's will be sent.      Host1 (perhaps): IAC SB STATUS SEND IAC SE      Host2 (the following stream is broken into multiple lines only for       readability. No carriage returns are implied.):         IAC SB STATUS IS         WILL ECHO         DO SUPPRESS-GO-AHEAD         WILL STATUS         DO STATUS         WILL RCTE         SB RCTE <11><1><24> SE         DO NAOL         SB NAOL DS <66> SE         IAC SE      Explanation of Host2's perceptions: It is responsible for echoing back       the data characters it receives over the Telnet connection; it will not       send Go-Ahead signals; it will both issue and request Status information;      it will send instruction for controlling the other side's terminal       printer; it will discuss the line width for data it is sending.