Gopher (protocol)

The Gopher protocol /ˈɡoʊfər/ is a TCP/IP application layer protocol designed for distributing, searching, and retrieving documents over the Internet. Strongly oriented towards a menu-document design, the Gopher protocol was a predecessor of (and later, an alternative to) the World Wide Web.

The protocol offers some features not natively supported by the Web and imposes a much stronger hierarchy on information stored on it. Its text menu interface is easy to use,^[1] and 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.^[1] Gopher was preferred by many network administrators for using fewer network resources than Web services.^[2]

With its hierarchical structure, Gopher provided a useful platform for the first large-scale electronic library connections.^[3] Gopher users remember the system as being "faster and more efficient and so much more organised" than today's Web services.^[4] Although largely supplanted by the Web in the years following, the Gopher protocol is still in use by enthusiasts, and a small population of actively-maintained servers remains.

Origins

The original Gopher system was released in late spring of 1991 by Mark McCahill, Farhad Anklesaria, Paul Lindner, Daniel Torrey, and Bob Alberti of the University of Minnesota.^[5] 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.

Gopher combines document hierarchies with collections of services, including WAIS, the Archie and Veronica search engines, and gateways to other information systems such as FTP and Usenet.

The general interest in Campus-Wide Information Systems (CWISs)^[6] in higher education at the time, and the ease with which a Gopher server could be set up to create an instant CWIS with links to other sites' online directories and resources were the factors contributing to Gopher's rapid adoption. By 1992, the standard method of locating someone's e-mail address was to find their organization's CCSO nameserver entry in Gopher, and query the nameserver.^[7]

The name was coined by Anklesaria^[8] as a play off of several meanings of the word "gopher." The University of Minnesota mascot is the gopher,^[9] a gofer (same sound) is an assistant who "goes for" things, and a gopher burrows through the ground to reach a desired location.

Stagnation

The World Wide Web was in its infancy in 1991, and Gopher services quickly became established. By the late 1990s, Gopher had largely 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.^[10] As a consequence of this, some users were concerned that a licensing fee would also be charged for independent implementations.^[11][12] Users were scared away from Gopher technology, to the advantage of the Web, which CERN disclaimed ownership of.^[13] The University of Minnesota later re-licensed its Gopher software under the GNU GPL.^[14]
• Gopher client functionality was quickly duplicated by early Web browsers, such as Mosaic, which subsumed the protocol as part of their functions.
• Gopher has a more rigid structure compared to the free-form HTML of the Web. With Gopher, every 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 typical user might traverse documents on the Web.

Gopher remains in active use by its enthusiasts, and there have been attempts to revive the use of Gopher on modern platforms and mobile devices. One such attempt is The Overbite Project, which hosts various browser extensions and modern clients.

As of 2010^[update], there are approximately 150 gopher servers indexed by Veronica-2,^[15] reflecting a slow growth from 2007 when there were fewer than 100,^[16] although many are infrequently updated. A handful of new servers are set up every year by hobbyists — over 50 have been set up and added to Floodgap's list since 1999.^[17] A snapshot of Gopherspace as it was in 2007 was circulated on BitTorrent and is still available.^[18] 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.^[19][20]

Native Gopher support

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 and 6 for Windows in June 2002 by a patch meant to fix a security vulnerability in the browser's Gopher protocol handler; however, it can be re-enabled by editing the Windows registry. In Internet Explorer 7, Gopher support was removed on the WinINET level.^[27]

Gopher browser plugins

For Mozilla Firefox and SeaMonkey, OverbiteFF extends Gopher browsing and supports Firefox 4. It includes support for accessing Gopher servers not on port 70 using a whitelist and for CSO/ph queries, and allows versions of Firefox and SeaMonkey that do not support Gopher natively to access Gopher servers. Plugins are also available for Konqueror^[28] and a proxy-based extension for Google Chrome.^[29]

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 (PDAs),^[30] 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. An application for Android 1.5+^[29] is in development and was released in alpha stage.^[31] A Java ME client is also available for compatible devices.^[32]

Other Gopher clients

Gopher was at its height of popularity during a time when there were still many equally competing computer architectures and operating systems. As such, 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 MOO object. 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, Gopher Proxy, and the WikkaGopher 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.

Gopher characteristics

As part of its design goals, Gopher functions and appears much like a mountable read-only global network file system (and software, such as gopherfs, is available that can actually mount a Gopher server as a FUSE resource). At a minimum, whatever a person can do with data files on a CD-ROM, they 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.

The top level menu of a Gopher server. Selecting the "Fun and Games" menu item...		...takes the user to the "Fun and Games" menu.

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.

Technical details

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    (NULL)  0
icities, counties, and geographical areas.  It has      fake    (NULL)  0
ilatitude/longitude, population, land and water area,   fake    (NULL)  0
iand ZIP codes. fake    (NULL)  0
i       fake    (NULL)  0
iTo search for a city, enter the city's name.  To search        fake    (NULL) 0
ifor a county, use the name plus County -- for instance,        fake    (NULL) 0
iDallas County. fake    (NULL)  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 (a "CR + LF" sequence). 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 (i.e., a period character) 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.^[5]

All lines in a gopher menu are terminated by "CR + LF", and consist of five fields: the item type as the very first character (see below), the display string (i.e., the description text to display), a selector (i.e., a file-system pathname), host name (i.e., the domain name of the server on which the item resides), and port (i.e., the port number used by that server). 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.^[33]

Gopher item types

Item types are described in gopher menus by a single number or (case specific) letter and act as hints to the client to tell it how to handle a specific media type in a menu, analogous to a MIME type. Every client necessarily must understand itemtypes 0 and 1. All known clients understand item types 0 through 9, g, and s, and all but the very oldest also understand file-types h and i.

• 0 = plain text file
• 1 = directory menu listing
• 2 = CSO search query
• 3 = error message
• 4 = BinHex encoded text file
• 5 = binary archive file
• 6 = UUEncoded text file
• 7 = search engine query
• 8 = telnet session pointer
• 9 = binary file
• g = GIF image
• h = HTML file
• i = informational message
• I = Image file of unspecified format. Client decides how to display. Often used for JPEG images.
• s = Audio file format, primarily a WAV file
• T = tn3270 session pointer

A list of additional file-type definitions has continued to evolve over time, with some clients supporting them and others not. As such, many servers assign the generic 9 to every binary file, hoping that the client's computer will be able to correctly process the file.

URL links

Historically, to create a link to a Web server, "GET /" was used as a pseudo-selector to simulate an HTTP client request. John Goerzen created an addition^[34] 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 "h", the display string is the title of the link, the item selector is "URL:http://gopher.quux.org/", and the domain and port are that of the originating Gopher server (so that clients that do not support URL links will query the server and receive an HTML redirection page).

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.

Gopher 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.

• gopherfs — a gopher filesystem FUSE abstraction

See also

Computer Science portal

References

External links

• List of all public Gopher servers (proxied link)
• List of public Gopher server uptimes (gopher link) (HTTP link)
• An announcement of Gopher on the Usenet Oct 8 1991
• Why is Gopher Still Relevant? A position statement on Gopher's survival.
• An article published by the technology discussion site "Ars Technica", about the Gopher community of enthusiasts nowadays
• Sites inspired by gopher: Spencer Hunter's Homepage — Example of a Gopher emulation in HTML, online since 1995. Under the "About this gopher and myself" directory is the author's own Gopher manifesto, "Why gopher is superior to the Web."; A community server for the Collier County, FL (Naples, FL) area whose fast web interface is inspired by Gopher. It is also an example of a Gopher emulation in HTML

Standards

• IANA Port Number allocations
• RFC 1436 — The Internet Gopher Protocol (a distributed document search and retrieval protocol)
• RFC 1580 — Guide to Network Resource Tools
• RFC 1689 — Networked Information Retrieval: Tools and Groups
• RFC 1738 — Uniform Resource Locators (URL)
• RFC 1808 — Relative Uniform Resource Locators
• RFC 2396 — Uniform Resource Identifiers (URI): Generic Syntax
• RFC 4266 — The gopher URI Scheme