RFC 4266

The gopher URI Scheme

📅 published November 2005, from ietf

RFC 4266: The gopher URI Scheme 🐿️✨

Okay bestie, here's the tea 🫖 This is RFC 4266, called "The gopher URI Scheme" 🎀. Paul Hoffman from the VPN Consortium wrote it 💅 and it came out in November 2005 🌸. It's on the Standards Track 🌈 and it obsoletes RFC 1738 👑, which is the big reason it exists at all.

Status of This Memo ✨

This document is an Internet standards track protocol for the Internet community, and it's basically asking everyone to talk about it and suggest improvements 💬. For the standardization state and status of this protocol, check the current edition of the "Internet Official Protocol Standards" (STD 1) 📖. Distribution of this memo is unlimited 🦋.

Copyright (C) The Internet Society (2005) 💜.

Abstract 🍓

Okay so this document specifies the gopher Uniform Resource Identifier (URI) scheme, which was first specified in RFC 1738 🐿️. The whole point is to let RFC 1738 be made obsolete while the gopher info stays on the standards track. Main character energy 👑.

1. Introduction 🌸

URIs were first defined in RFC 2396 [RFC2396], and then RFC 3986 [RFC3986] updated that. Both of those documents also explain how to define schemes for URIs 🫶.

The first definition for a lot of URI schemes showed up in RFC 1738 [RFC1738]. Since that document is now obsolete, this one copies the gopher URI scheme over from it so the material can stay on standards track 💖.

2. Scheme Definition 🧚

The gopher URL scheme is used to point at Internet resources you can reach with the Gopher protocol 🐿️✨.

The base Gopher protocol is described in RFC 1436 [RFC1436]. It supports items and collections of items (directories) 📁. Gopher+ is a set of upward-compatible extensions to the base Gopher protocol and is described in [Gopher+] 🎀. It lets you attach arbitrary sets of attributes and alternate data representations to Gopher items, and Gopher URLs cover both Gopher and Gopher+ items and their attributes 💅.

Historical note: The Gopher protocol was everywhere in the early 1990s, but hardly any Gopher servers are still running today 🥲.

2.1. Gopher URL Syntax 🦋

A Gopher URL takes this form:

gopher://<host>:<port>/<gopher-path>

where <gopher-path> is one of:

<gophertype><selector>
<gophertype><selector>%09<search>
<gophertype><selector>%09<search>%09<gopher+_string>

If :<port> is left out, the port defaults to 70 🔥. <gophertype> is a single-character field that says what Gopher type the URL's resource is 🧩. The whole <gopher-path> can also be empty. In that case the delimiting "/" is optional too, and <gophertype> defaults to "1" ✨.

<selector> is the Gopher selector string. In the Gopher protocol it's a sequence of octets that can hold any octets except 09 hexadecimal (US-ASCII HT or tab), 0A hexadecimal (US-ASCII character LF), and 0D (US-ASCII character CR) 🙈.

Gopher clients pick which item they want by sending the Gopher selector string to a Gopher server 📬.

Inside the <gopher-path>, no characters are reserved 🌈.

Heads up, some Gopher <selector> strings start with a copy of the <gophertype> character. When that happens, the character shows up twice in a row 👯. The Gopher selector string can also be an empty string, and that's how Gopher clients refer to the top-level directory on a Gopher server 🏠.

2.2. Specifying URLs for Gopher Search Engines 🔍

If the URL is pointing at a search that gets submitted to a Gopher search engine, the selector is followed by an encoded tab (%09) and then the search string 🫧. To submit that search, the Gopher client sends the <selector> string (after decoding it), a tab, and the search string to the Gopher server 💌.

2.3. URL Syntax for Gopher+ Items 💜

Historical note: Gopher+ was uncommon even back when regular Gopher was popular 😭.

URLs for Gopher+ items get a second encoded tab (%09) and a Gopher+ string. In this case the %09<search> part must be included, even though the <search> element is allowed to be the empty string 🙃.

The <gopher+_string> carries the info needed to retrieve the Gopher+ item. Gopher+ items can have alternate views and arbitrary sets of attributes, and they can also have electronic forms attached 🧾.

To grab the data behind a Gopher+ URL, a client connects to the server and sends the Gopher selector, then a tab and the search string (which can be empty), then another tab and the Gopher+ commands 🎬.

2.4. Default Gopher+ Data Representation 🎨

When a Gopher server sends a directory listing to a client, its Gopher+ items get tagged with either a "+" (meaning Gopher+ items) or a "?" (meaning Gopher+ items that have a +ASK form attached) 🏷️. A Gopher URL whose Gopher+ string is only a "+" points at the default view (data representation) of the item. A Gopher+ string that's only a "?" points at an item with a Gopher electronic form attached 💅.

2.5. Gopher+ Items with Electronic Forms 📝

Gopher+ items with a +ASK attached (the ones tagged with "?") need the client to fetch the item's +ASK attribute to get the form definition 📋. Then the client asks the user to fill out the form, and sends the user's answers back along with the selector string to get the item 🙌. Gopher+ clients already know how to do all this, but they rely on the "?" tag in the item description to know when to handle it 🧠. The "?" shows up in the Gopher+ string because it matches how the Gopher+ protocol uses that symbol 🔁.

2.6. Gopher+ Item Attribute Collections 🗂️

To refer to a Gopher+ item's attributes, the Gopher URL's Gopher+ string is "!" or "$". "!" means all of one item's Gopher+ attributes 🎯. "$" means all the item attributes for every item in a Gopher directory 🌟.

2.7. Referring to Specific Gopher+ Attributes 🔖

To point at specific attributes, the URL's gopher+_string is "!<attribute_name>" or "$<attribute_name>" 🎀. For example, to get the attribute holding an item's abstract, the gopher+_string would be "!+ABSTRACT" 📄.

To refer to several attributes at once, the gopher+_string is the attribute names separated by coded spaces. For example, "!+ABSTRACT% 20+SMELL" refers to the +ABSTRACT and +SMELL attributes of an item 👃✨.

2.8. URL Syntax for Gopher+ Alternate Views 🌍

Gopher+ lets items have optional alternate data representations (alternate views) 🖼️. To get one, a Gopher+ client sends the right view and language identifier, which you can find in the item's +VIEW attribute 🔑. To point at a specific alternate view, the URL's Gopher+ string looks like this:

+<view_name>%20<language_name>

For example, a Gopher+ string of "+application/postscript%20Es_ES" refers to the Spanish-language postscript alternate view of a Gopher+ item 🇪🇸💕.

2.9. URL Syntax for Gopher+ Electronic Forms 📑

The gopher+_string for a URL pointing at an item referenced by a Gopher+ electronic form (an ASK block) that's been filled out with specific values is a coded version of what the client sends to the server 🫧. The gopher+_string looks like this:

+%091%0D%0A+-1%0D%0A<ask_item1_value>%0D%0A
<ask_item2_value>%0D%0A.%0D%0A

To retrieve this item, the Gopher client sends the following text to the Gopher server:

<a_gopher_selector><tab>+<tab>1<cr><lf>
+-1<cr><lf>
<ask_item1_value><cr><lf>
<ask_item2_value><cr><lf>
.<cr><lf>

3. Security Considerations 🔐

Okay, security is serious, so listen up 🚨. There are lots of security considerations for URI schemes, and they're discussed in [RFC3986] 📚. The Gopher protocol uses passwords in the clear for authentication and offers no privacy, and both of those are considered extremely unsafe in current practice 💀😭.

4. Informative References 📚

[Gopher+] Anklesaria, F., et al., "Gopher+: Upward compatible enhancements to the Internet Gopher protocol", University of Minnesota, July 1993, <ftp://boombox.micro.umn.edu/pub/gopher/gopher_protocol/Gopher+/Gopher+.txt> 🐿️

[RFC1738] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform Resource Locators (URL)", RFC 1738, December 1994. 🌸

[RFC2396] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. 🌷

[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. 💖

[RFC1436] Anklesaria, F., McCahill, M., Lindner, P., Johnson, D., Torrey, D., and B. Albert, "The Internet Gopher Protocol (a distributed document search and retrieval protocol)", RFC 1436, March 1993. 🧚

Author's Address 🎀

Paul Hoffman
VPN Consortium
127 Segre Place
Santa Cruz, CA  95060
US

EMail: paul.hoffman@vpnc.org

Copyright (C) The Internet Society (2005).

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