RFC 735 DHC RHG 3 Nov 77 42083 Telnet Byte Macro Option Network Working Group David H. Crocker RFC: #735 Rand-ISD NIC: #42083 (Dcrocker at Rand-Unix) Richard H. Gumpertz Carnegie-Mellon University (Gumpertz at CMU-10A) Obsoletes: RFC #729 (NIC #40306) 3 November 1977 Revised TELNET Byte Macro Option 1. Command name and code: BM 19 2. Command Meanings: IAC WILL BM The sender of this command REQUESTS or AGREES to use the BM option, and will send single data characters which are to be interpreted as if replacement data strings had been sent. IAC WON'T BM The sender of this option REFUSES to send single data characters which are to be interpreted as if replacement data strings had been sent. Any existing BM definitions are discarded (i.e., reset to their original data interpretations). IAC DO BM The sender REQUESTS or AGREES to have the other side (sender of WILL BM) send single data characters which are to be interpreted as if replacement data strings had been sent. IAC DON'T BM The sender REFUSES to allow the other side to send single data characters which are to be interpreted as if replacement data strings had been sent. Any existing BM definitions are to be discarded. 1 RFC 735 DHC RHG 3 Nov 77 42083 Telnet Byte Macro Option IAC SB BM IAC SE where: is the data byte actually to be sent across the network; it may NOT be Telnet IAC (decimal 255, but may be any other 8-bit character. is one 8-bit byte binary number, indicating how many characters follow, up to the ending IAC SE, but not including it. Note that doubled IACs in the definition should only be counted as one character per pair. is a string of zero or more Telnet ASCII characters and/or commands, which the is to represent; any character may occur within a . Note, however, that an IAC in the string must be doubled, to be interpreted later as an IAC; to be interpreted later as data byte 255, it must be quadrupled in the original specification. The indicated will be sent instead of the indicated . The receiver of the (the sender of the DO BM) is to behave EXACTLY as if the string of bytes had instead been received from the network. This interpretation is to occur before any other Telnet interpretations, unless the occurs as part of a Telnet command; in this case no special interpretation is to be made. In particular, an entire Telnet subnegotiation (i.e. from IAC SB through IAC SE) is to be considered a Telnet command in which NO replacement should be done. The effect of a particular may be negated by reseting it to "expand" into itself. IAC SB BM X <0> IAC SE may be used to cause X to be ignored in the data stream. is decimal 1. IAC SB BM IAC SE The receiver of the for accepts the requested definition and will perform the indicated replacement whenever a is received and is not part of any IAC Telnet command sequence. 2 RFC 735 DHC RHG 3 Nov 77 42083 Telnet Byte Macro Option is decimal 2. IAC SB BM IAC SE The receiver of the for refuses to perform the indicated translation from to because the particular is not an acceptable choice, the length of the exceeds available storage, the length of the actual did not match the length predicted in the , or for some unspecified reason. is decimal 3. may be which is decimal 1; (for receiver's storage) which is decimal 2; (of actual string compared with promised length in ) which is decimal 3; or (intended for use only until this document can be updated to include reasons not anticipated by the authors) which is decimal zero (0). IAC SB BM IAC SE The is to be treated as real data, rather than as representative of the Note that this subcommand cannot be used during Telnet subcommands, since subcommands are defined to end with the next occurrence of "IAC SE". Including this BM subcommand within any Telnet subcommand would therefore prematurely terminate the containing subcommand. is decimal 4. IAC SB BM IAC SE The RECEIVER of the defined (i.e., the sender of IAC DO BM) requests the sender of to cancel its definition. is the same as for the subcommand. 3 RFC 735 DHC RHG 3 Nov 77 42083 Telnet Byte Macro Option The sender should (but is not required to) respond by resetting (i.e., sending an IAC SB BM <1> IAC SE). If the receiver absolutely insists on cancelling a given macro, the best it can do is to turn off the entire option, with IAC DONT BM, wait for an acknowledging IAC WONT BM and then restart the option, with IAC DO BM. This will reset all other macroes as well but it will allow the receiver to REFUSE with code BAD CHOICE if/when the foreign site attempts to redefine the macro in question. 3. Default: WON'T BM -- DON'T BM No reinterpretation of data bytes is done. 4. Motivation for the option: Subcommands for Telnet options currently require a minimum of five characters to be sent over the network (i.e., IAC SB