RFC 1096

RFC 1096: Telnet X Display Location Option 🎀

Okay bestie, this is RFC 1096, and it's giving classic networking legend 🦋 It's by Glenn A. Marcy at Carnegie Mellon University, and it came out in March 1989 ✨ The title block doesn't mention obsoleting or updating any other RFC, so it's a solo act 💅

Status of This Memo ✨

ngl this is the official "who's this for" part. It says this RFC specifies a standard for the Internet community 🌈 Hosts on the Internet that send 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 here is copied from that RFC, so it's not a total glow-up from scratch 🫶

Motivation 🌸

Picture this: you're running the Telnet client under the X window system, and it's so iconic when the remote Telnet actually knows your X display location 🖥️ Like, the user might wish to start other X applications from the remote host using the same display location as the Telnet client ✨ That's the whole purpose of this option. It makes that info available through telnet connections 💜

1. Command Name and Code 💖

The command is called X-DISPLAY-LOCATION, but you'll also see it shortened to XDISPLOC. Its code is 35 🔥

X-DISPLAY-LOCATION (XDISPLOC)

Code = 35

2. Command Meanings 🧚

Here's what each message means, no cap 💅

IAC WILL X-DISPLAY-LOCATION

The sender is willing to send the X display location in a subsequent sub-negotiation ✨

IAC WON'T X-DISPLAY-LOCATION

The sender refuses to send the X display location 🙈

IAC DO X-DISPLAY-LOCATION

The sender is willing to receive the X display location in a subsequent sub-negotiation 🌸

IAC DON'T X-DISPLAY-LOCATION

The sender refuses to accept the X display location 💀

IAC SB X-DISPLAY-LOCATION SEND IAC SE

The sender requests the receiver to transmit his (the receiver's) X display location. The code for SEND is 1. (See below.) It's giving "may I please see your location" energy 🥺

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

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

3. Default 🍓

These are the defaults, so if nobody says anything fancy, this is what happens:

WON'T X-DISPLAY-LOCATION

The X display location will not be exchanged. Rip to the location 😭

DON'T X-DISPLAY-LOCATION

The X display location will not be exchanged. Same energy, bestie 💅

4. Description of the Option 💅

Okay so, WILL and DO are only used to get and give permission for future discussion. The actual swapping of status info happens inside the option subcommands, which look like 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 the actual X display location (inside an IAC SB X-DISPLAY-LOCATION IS ... IAC SE command). The X display location may not be sent spontaneously. It only goes out 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. Clean girl aesthetic only ✨

Here's an example of the option in action 🌈

Host1: IAC DO X-DISPLAY-LOCATION

Host2: IAC WILL X-DISPLAY-LOCATION

(Host1 is now free to request status information at any time. Free bird era 🕊️)

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. Math ate that up 🧮)

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. Bestie, the client has to do a little glow-up first 💖

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 💜