Gopher (protocol)
The Gopher protocol is a communications protocol designed for distributing, searching, and retrieving documents in Internet Protocol networks. The design of the Gopher protocol and user interface is menu-driven, and presented an alternative to the World Wide Web in its early stages, but ultimately fell into disfavor, yielding to the Hypertext Transfer Protocol. The Gopher ecosystem is often regarded as the effective predecessor of the World Wide Web.
The protocol was invented by a team led by Mark P. McCahill at the University of Minnesota. It offers some features not natively supported by the Web and imposes a much stronger hierarchy on the documents it stores. Its text menu interface is well-suited to computing environments that rely heavily on remote text-oriented computer terminals, which were still common at the time of its creation in 1991, and the simplicity of its protocol facilitated a wide variety of client implementations. More recent Gopher revisions and graphical clients added support for multimedia. Gopher was preferred by many network administrators for using fewer network resources than Web services.
Gopher's hierarchical structure provided a platform for the first large-scale electronic library connections. The Gopher protocol is still in use by enthusiasts, and although it has been almost entirely supplanted by the Web, a small population of actively-maintained servers remains.
Origins
Gopher system was released in mid-1991 by Mark P. McCahill, Farhad Anklesaria, Paul Lindner, Daniel Torrey, and Bob Alberti of the University of Minnesota in the United States. Its central goals were, as stated in RFC 1436:- A file-like hierarchical arrangement that would be familiar to users.
- A simple syntax.
- A system that can be created quickly and inexpensively.
- Extending the file system metaphor, such as searches.
The general interest in campus-wide information systems in higher education at the time, and the ease of setup of Gopher servers to create an instant CWIS with links to other sites' online directories and resources were the factors contributing to Gopher's rapid adoption.
The name was coined by Anklesaria as a play on several meanings of the word "gopher". The University of Minnesota mascot is the gopher, a gofer is an assistant who "goes for" things, and a gopher burrows through the ground to reach a desired location.
Decline
The World Wide Web was in its infancy in 1991, and Gopher services quickly became established. By the late 1990s, Gopher had ceased expanding. Several factors contributed to Gopher's stagnation:- In February 1993, the University of Minnesota announced that it would charge licensing fees for the use of its implementation of the Gopher server. Users became concerned that fees might also be charged for independent implementations. Gopher expansion stagnated, to the advantage of the World Wide Web, to which CERN disclaimed ownership. In September 2000, the University of Minnesota re-licensed its Gopher software under the GNU General Public License.
- Gopher client functionality was quickly duplicated by the early Mosaic web browser, which subsumed its protocol.
- Gopher has a more rigid structure than the free-form HTML of the Web. Every Gopher document has a defined format and type, and the typical user navigates through a single server-defined menu system to get to a particular document. This can be quite different from the way a user finds documents on the Web.
Server census
- , there remained about 160 gopher servers indexed by Veronica-2, reflecting a slow growth from 2007 when there were fewer than 100. They are typically infrequently updated. On these servers Veronica indexed approximately 2.5 million unique selectors. A handful of new servers were being set up every year by hobbyists with over 50 having been set up and added to Floodgap's list since 1999. A snapshot of Gopherspace in 2007 circulated on BitTorrent and was still available in 2010. Due to the simplicity of the Gopher protocol, setting up new servers or adding Gopher support to browsers is often done in a tongue-in-cheek manner, principally on April Fools' Day.
- In November 2014 Veronica indexed 144 gopher servers, reflecting a small drop from 2012, but within these servers Veronica indexed approximately 3 million unique selectors.
- In March 2016 Veronica indexed 135 gopher servers, within which it indexed approximately 4 million unique selectors.
- In March 2017 Veronica indexed 133 gopher servers, within which it indexed approximately 4.9 million unique selectors.
- In May 2018 Veronica indexed 260 gopher servers, within which it indexed approximately 3.7 million unique selectors.
- In May 2019 Veronica indexed 320 gopher servers, within which it indexed approximately 4.2 million unique selectors.
- In January 2020 Veronica indexed 395 gopher servers, within which it indexed approximately 4.5 million unique selectors.
Technical details
Gopher characteristics
Gopher is designed to function and to appear much like a mountable read-only global network file system. At a minimum, whatever a person can do with data files on a CD-ROM, one can do on Gopher.A Gopher system consists of a series of hierarchical hyperlinkable menus. The choice of menu items and titles is controlled by the administrator of the server.
Similar to a file on a Web server, a file on a Gopher server can be linked to as a menu item from any other Gopher server. Many servers take advantage of this inter-server linking to provide a directory of other servers that the user can access.
Protocol
The Gopher protocol was first described in RFC 1436. IANA has assigned TCP port 70 to the Gopher protocol.The protocol is simple to negotiate, making it possible to browse without using a client. A standard gopher session may therefore appear as follows:
/Reference
1CIA World Factbook /Archives/mirrors/textfiles.com/politics/CIA gopher.quux.org 70
0Jargon 4.2.0 /Reference/Jargon 4.2.0 gopher.quux.org 70 +
1Online Libraries /Reference/Online Libraries gopher.quux.org 70 +
1RFCs: Internet Standards /Computers/Standards and Specs/RFC gopher.quux.org 70
1U.S. Gazetteer /Reference/U.S. Gazetteer gopher.quux.org 70 +
iThis file contains information on United States fake 0
icities, counties, and geographical areas. It has fake 0
ilatitude/longitude, population, land and water area, fake 0
iand ZIP codes. fake 0
i fake 0
iTo search for a city, enter the city's name. To search fake 0
ifor a county, use the name plus County -- for instance, fake 0
iDallas County. fake 0
Here, the client has established a TCP connection with the server on port 70, the standard gopher port. The client then sends a string followed by a carriage return followed by a line feed. This is the selector, which identifies the document to be retrieved. If the item selector were an empty line, the default directory would be selected. The server then replies with the requested item and closes the connection. According to the protocol, before the connection is closed, the server should send a full-stop on a line by itself. However, as is the case here, not all servers conform to this part of the protocol and the server may close the connection without returning the final full-stop.
In this example, the item sent back is a gopher menu, a directory consisting of a sequence of lines each of which describes an item that can be retrieved. Most clients will display these as hypertext links, and so allow the user to navigate through gopherspace by following the links.
All lines in a gopher menu are terminated by "CR + LF", and consist of five fields: the item type as the very first character, the display string, a selector, host name, and port. The item type and display string are joined without a space; the other fields are separated by the tab character.
Because of the simplicity of the Gopher protocol, tools such as netcat make it possible to download Gopher content easily from the command line:
echo jacks/jack.exe | nc gopher.example.org 70 > jack.exe
The protocol is also supported by cURL as of 7.21.2-DEV.
Search request
The selector string in the request can optionally be followed by a tab character and a search string. This is used by item type 7.Item types
In a Gopher menu's source code, a one-character code indicates what kind of content the client should expect. This code may either be a digit or a letter of the alphabet; letters are case-sensitive.The technical specification for Gopher, RFC 1436, defines 14 item types. A one-character code indicates what kind of content the client should expect. Item type is an error code for exception handling. Gopher client authors improvised item types , , and after the publication of RFC 1436. Browsers like Netscape Navigator and early versions of Microsoft Internet Explorer would prepend the item type code to the selector as described in RFC 4266, so that the type of the gopher item could be determined by the url itself. Most gopher browsers still available, use these prefixes in their urls.
URL links
Historically, to create a link to a Web server, "GET /" was used as a pseudo-selector to emulate an HTTP GET request. John Goerzen created an addition to the Gopher protocol, commonly referred to as "URL links", that allows links to any protocol that supports URLs. For example, to create a link to http://gopher.quux.org/, the item type is, the display string is the title of the link, the item selector is "Related technology
The master Gopherspace search engine is Veronica. Veronica offers a keyword search of all the public Internet Gopher server menu titles. A Veronica search produces a menu of Gopher items, each of which is a direct pointer to a Gopher data source. Individual Gopher servers may also use localized search engines specific to their content such as Jughead and Jugtail.GopherVR is a 3D virtual reality variant of the original Gopher system.
Client software
Web browsers
Browsers that do not natively support Gopher can still access servers using one of the available Gopher to HTTP gateways.Gopher support was disabled in Internet Explorer versions 5.x and 6 for Windows in August 2002 by a patch meant to fix a security vulnerability in the browser's Gopher protocol handler to reduce the attack surface which was included in IE6 SP1; however, it can be re-enabled by editing the Windows registry. In Internet Explorer 7, Gopher support was removed on the WinINET level.
Gopher browser extensions
For Mozilla Firefox and SeaMonkey, Overbite extensions extend Gopher browsing and support the current versions of the browsers :- OverbiteWX redirects
gopher:// URLs to a proxy; - OverbiteNX adds native-like support;
- for Firefox up to 56.*, and equivalent versions of SeaMonkey, OverbiteFF adds native-like support.
For Chromium and Google Chrome, Burrow is available. It redirects
For Konqueror, Kio gopher is available.
Gopher clients for mobile devices
Some have suggested that the bandwidth-sparing simple interface of Gopher would be a good match for mobile phones and personal digital assistants, but so far, mobile adaptations of HTML and XML and other simplified content have proven more popular. The PyGopherd server provides a built-in WML front-end to Gopher sites served with it.The early 2010s saw a renewed interest in native Gopher clients for popular smartphones: Overbite, an open source client for Android 1.5+ was released in alpha stage in 2010. PocketGopher was also released in 2010, along with its source code, for several Java ME compatible devices. Gopher Client was released in 2016 as a proprietary client for iPhone and iPad devices and is currently maintained.
Other Gopher clients
Gopher popularity was at its height at a time when there were still many equally competing computer architectures and operating systems. As a result, there are several Gopher clients available for Acorn RISC OS, AmigaOS, Atari MiNT, CMS, DOS, classic Mac OS, MVS, NeXT, OS/2 Warp, most UNIX-like operating systems, VMS, Windows 3.x, and Windows 9x. GopherVR was a client designed for 3D visualization, and there is even a Gopher client in MOO. The majority of these clients are hard-coded to work on TCP port 70.Gopher to HTTP gateways
Users of Web browsers that have incomplete or no support for Gopher can access content on Gopher servers via a server gateway or proxy server that converts Gopher menus into HTML; known proxies are the Floodgap Public Gopher proxy and Gopher Proxy. Similarly, certain server packages such as GN and PyGopherd have built-in Gopher to HTTP interfaces. Squid Proxy software gateways any gopher:// URL to HTTP content, enabling any browser or web agent to access gopher content easily.Server software
Because the protocol is trivial to implement in a basic fashion, there are many server packages still available, and some are still maintained.| Server | Developed by | Latest version | Release date | License | Written in | Notes |
| Rob Linwood | 1.0.1 | MIT | Java | |||
| Timm Murray | 0.1 | GPL | Perl | Apache 2 plugin to run [|Gopher-Server]. | ||
| Charles Childers | 2017.4 | ISC | Forth | |||
| Bucktooth | Cameron Kaiser | 0.2.9 | Floodgap Free Software License | Perl | ||
| Michael Lazar | 2.2.1 | GPLv3 | Python | |||
| Quinn Evans | 0.0.1 | 2-clause BSD | Common Lisp | |||
| Christoph Lohmann | 0.34 | MIT | C | |||
| 2.25-20020226 | GPL | C | ||||
| Sean MacLennan | 1.2 | GPLv2 | C | |||
| Geoff Sevart | 1.07 | Freeware | .NET 3.5 | Version 1.06 of 26 August 2010 is available from . | ||
| Timm Murray | 0.1.1 | GPL | Perl | |||
| Kim Holviala and others | 3.1 | BSD | C | |||
| Guillaume Duhamel | 0.2.3 | GPL | C | |||
| 0.5 | GPLv3 | FreeBASIC | Version 0.4 is available from . | |||
| Aaron W. Hsu | 8.0 | ISC | Scheme | |||
| Mate Nagy | 1.1 | GPLv3 | C | |||
| Mateusz Viste | 1.0.12 | GPLv3 | C | |||
| dotcomboom | 1.1 | BSD 2-Clause | Python | Python-based Gopher library with both server and client support | ||
| PyGopherd | John Goerzen | 2.0.18.5 | GPL | Python | ||
| Adam Gurno | 0.3.5 | GPLv2 | Python | Development stopped as of 17 April 2003 | ||
| Salvatore Sanfilippo | 6.0.6 | BSD 3 Clause | C | |||
| Lukas Epple | 0.2.1.1 | GPL | Haskell | |||
| Nathaniel Leveck | 0.0.1 | BSD | FreeBASIC |