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Network Working Group G. Marcy Request for Comments: 1096 Carnegie Mellon University

                                                            March 1989

                  Telnet X Display Location Option

Status of This Memo

 This RFC specifies a standard for the Internet community.  Hosts on
 the Internet that transmit the X display location within the Telnet
 protocol are expected to adopt and implement this standard.
 Distribution of this memo is unlimited.

 This standard is modelled on RFC 1079 [1], the telnet terminal speed
 option.  Much of the text of this document is copied from that RFC.

Motivation

 When a user is running the Telnet client under the X window system,
 it is useful for the remote Telnet to know the X display location of
 that client.  For example, the user might wish to start other X
 applications from the remote host using the same display location as
 the Telnet client.  The purpose of this option is to make this
 information available through telnet connections.

1. Command Name and Code

    X-DISPLAY-LOCATION (XDISPLOC)

    Code = 35

2. Command Meanings

    IAC WILL X-DISPLAY-LOCATION

       Sender is willing to send the X display location in a
       subsequent sub-negotiation.

    IAC WON'T X-DISPLAY-LOCATION

       Sender refuses to send the X display location.

    IAC DO X-DISPLAY-LOCATION

       Sender is willing to receive the X display location in a
       subsequent sub-negotiation.

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    IAC DON'T X-DISPLAY-LOCATION

       Sender refuses to accept the X display location.

    IAC SB X-DISPLAY-LOCATION SEND IAC SE

       Sender requests receiver to transmit his (the receiver's) X
       display location.  The code for SEND is 1.  (See below.)

    IAC SB X-DISPLAY-LOCATION IS ... IAC SE

       Sender is stating his X display location.  The code for IS is
       0.  (See below.)

3. Default

    WON'T X-DISPLAY-LOCATION

       The X display location will not be exchanged.

    DON'T X-DISPLAY-LOCATION

       The X display location will not be exchanged.

4. 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 X-DISPLAY-LOCATION...).

 Once the two hosts have exchanged a WILL and a DO, the sender of the
 DO X-DISPLAY-LOCATION is free to request the X display location.
 Only the sender of the DO may send requests (IAC SB X-DISPLAY-
 LOCATION SEND IAC SE) and only the sender of the WILL may transmit
 actual X display location (within an IAC SB X-DISPLAY-LOCATION IS ...
 IAC SE command).  The X display location may not be sent
 spontaneously, but only in response to a request.

 The X display location is an NVT ASCII string.  This string follows
 the normal Unix convention used for the DISPLAY environment variable,
 e.g.,

       <host>:<dispnum>[.<screennum>]

 No extraneous characters such as spaces may be included.

    The following is an example of use of the option:

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       Host1: IAC DO X-DISPLAY-LOCATION

       Host2: IAC WILL X-DISPLAY-LOCATION

    (Host1 is now free to request status information at any time.)

       Host1: IAC SB X-DISPLAY-LOCATION SEND IAC SE

       Host2: IAC SB X-DISPLAY-LOCATION IS "SRI-NIC.ARPA:0.0" IAC SE

    (This command is 22 octets.)

5. Implementation Suggestions

 Since the X display location may not contain a hostname on the client
 host, i.e., ":0" or "unix:0.0", the Telnet client will need to modify
 the location appropriately before sending it on to the remote Telnet.

Reference

 [1]  Hedrick, C., "Telnet Terminal Speed Option", RFC 1079,
      Rutgers University, December, 1988.

Author's Address:

 Glenn A. Marcy
 Carnegie Mellon University
 School of Computer Science
 Pittsburgh, PA 15213-3890

 Phone: (412) 268-7669

 Email: Glenn.Marcy@CS.CMU.EDU

Marcy [Page 3]