RFC 377 (rfc377) - Page 2 of 4

Using TSO via ARPA Network Virtual Terminal

RFC 377            Using TSO via Net Virtual Terminal        August 1972


    3.  When first connected to CCN server Telnet, the user has a choice
        of several commands besides "TSO". The TSO-related commands are:

            HELP    -  A listing of commands at this level, and other
                       general information.

            BBOARD  -  List operational notices.

    4.  Local echoing (i.e., by the user site) is required.

    5.  Server-Telnet will time-out and disconnect the user if:

        a.  Output to the Network does not complete within 5 minutes, or

        b.  An INS, DATA MARK pair does not match within 2 minutes, or

        c.  TSO waits for the user to enter input for 20 minutes.

B.  Conversing with TSO
    -------------------

    1.  TSO is strictly a line-at-a-time system.  Input is not scanned
        until either an end-of-line or an INS (interrupt) is received at
        CCN.  TSO sends the user an exclamation mark ("!") as a herald
        when waiting for input.

    2.  The end-of-line indication for input and output lines is the
        standard CR LF sequence.

    3.  The remote user my interrupt TSO output by sending an INS and
        DATA MARK (Telnet X'80').  Note to TIP users: this may be
        accomplished with the TIP command "SEND SYNC".  Each such
        interrupt is passed to TSO, which interprets it as an output
        break, i.e., as if the user pressed the ATTention key on his
        2741 while the keyboard was _locked_.

        On the Network, "attentions" are not used to delete lines being
        entered.  The CCN Server-Telnet provides line editing functions
        for TSO users: the ASCII control CAN deletes the line being
        entered, while BS deletes the preceding character.

    4.  There is a third interrupt case to be considered: suppose a
        program has placed the user's terminal into input state, but the
        user wants to suspend its execution and take control up a level
        without satisfying the pending input request.  This is supposed
        to be accomplished by sending an INS/DATA MARK pair.
        Unfortunately, due to a bug in our Network interface to TSO, the
        interrupt will be ignored in this case.  To circumvent this



Braden