Telnet logger/server for host LL-67(1)

　　Network Working Group J. Winett

　　Request for Comments: 466 LL-67

　　NIC: 14740 27 February 1973

　　Category: TELNET

　　TELNET LOGGER/SERVER For Host LL-67

    The attached writeup documents the TELNET LOGGER/SERVER for the　CP/CMS system on the Lincoln Laboratory 360>67 (host 10).

　　Use of the hide-your-input and noecho TELNET controls are used for　the EBCDIC print suppress (bypass) and print restore features during　the login procedure. To support half duplex terminals, the TELNET　　control break (reverse break) is sent as an input prompt when input　is desired. This code can also be used to indicate that a previous　line sent without an end of line sequence (CR-LF) should be printed.

　　This material has not been reviewed for public release and is　intended only for use with the ARPA network. It should not be quoted　or cited in any publication not related to the ARPA network.

　　Operation of the Lincoln Laboratory

　　CP/CMS TELNET LOGGER/SERVER

　　ICP Connection

　　The TELNET LOGGER/SERVER follows the ICP protocol for making a pair　of connections. The LOGGER is initially enabled for a connection on　socket X'00000001'. When an RFCis received for this socket a pair　of sockets will be chosen for the TELNET connections. If the maximum　number of TELNET users which can be served are active, the initial　connection is refused. Currently, three TELNET users can be served.

　　TELNET LOGGER

　　After the ICP connections have been setup, the LOGGER expects a　TELNET data type code, a string of network ASCII characters, or a　null line (just CR-LF) to indicate whether its operation should be in　ASCII or in EBCDIC character codes. ASCII is assumed unless the　first byte received is the TELNET EBCDIC data type code (X'A2). When　something has been received, the message:

　　Lincoln Laboratory CP/CMS Online　will be transmitted by the LOGGER. For example, if ASCII operation　is desired a null line (just CR-LF) transmitted on the send socket　will cause the welcoming message to be sent in ASCII. The CP login　procedure can then begin. If communications is desired to be carried　on with EBCDIC character codes, the first byte transmitted should be　the TELNET data type code for EBCDIC (X'A2'). Thereafter all　communications will be in the code originally used.

　　The CP login procedure expects the user to enter:

　　LOGIN userid　where the userid specifies the desired virtual machine. CP then　replies with:

　　ENTER PASSWORD:

　　followed by the EBCDIC code for bypass (x'24') which is mapped into　the TELNET code hide-your-input.

　　The user should then enter a password. Passwords entered from the　network may be different from those entered from a local terminal.

　　The LOGGER maps network passwords into a corresponding CP password.

　　Thus, accessto an account can only be made from the network if a　network password, together with a CP password and userid, is entered　into a file which is read by the LOGGER. If a userid entered from　the network is not in the LOGGER FILE (or if the network password　does not match the one included in the file for the specified userid)　the LOGGER passes an invalid userid (or password) to CP. The CP　response for an invalid userid or password is then sent to the　network user.

　　After a password is received by CP, CP transmits the EBCDIC code for　restore (X'14') which is mapped into the TELNET control noecho.

　　TELNET SERVER

　　Since the CP/CMS system operates with EBCDIC codes, ASCII codes must　be translated into EBCDIC before being sent to a virtual machine.

　　Figure 1 gives the ASCII codes and their EBCDIC mapping. When the　ASCII sequence CR-LF is received, it is mapped into the EBCDIC code　NL. Whenever the TELNET control NOP is included in an input string,　it is mapped into an EBCDIC idle (X'17') and then removed from the　string. Thus, if TELNET NOP codes are included between a CR and LF,　they are removed before the CR-LF is mapped into the EBCDIC NL.

　　The TELNET control hide-your-input is mapped into the EBCDIC code for　bypass (X'24') and the TELNET control echo is mapped into the EBCDIC　control for restore (X'14'). If the TELNET control echo is received,　the SERVER should send the control noecho but this feature has not　yet been implemented. Instead, the TELNET control echo is mapped　into the EBCDIC code X'23'. If the TELNET break is received, it is　interpreted as an attention signal and the appropriate action is　taken by CP or CMS.