protocol

Gopher (protocol)

For other uses, see [].

Gopher is a distributed document search and retrieval network protocol designed for the Internet. Its goal is to function as an improved form of Anonymous FTP, enhanced with hyperlinking features similar to that of the World Wide Web.

The Gopher 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 well-suited to computing environments that rely heavily on remote computer terminals, common in universities at the time of its creation in 1991 until 1993.

Origins

The original Gopher system was released in late spring of 1991 by Mark McCahill, Farhad Anklesaria, Paul Lindner, Dan Torrey, and Bob Alberti of the University of Minnesota. Its central goals are:

  • 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 to include things like searches

The source of the name "Gopher" is claimed to be threefold:

  1. Users instruct it to "go for" information
  2. It does so through a web of menu items analogous to [(animal)|gopher] holes
  3. The sports teams of the University of Minnesota are the Golden Gophers

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

The general interest in Campus-Wide Information Systems (CWISs) 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.

The exponential scaling of utility in social networked systems (Reed's law) seen in Gopher, and then the Web, is a common feature of networked hypermedia systems with distributed authoring. In 1993–1994, Web pages commonly contained large numbers of links to Gopher-delivered resources, as the Web continued Gopher's embrace and extend tradition of providing gateways to other services.

Stagnation

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. As a consequence of this some users suspected that a licensing fee would also be charged for independent implementations. In contrast, no such limitation has yet been imposed on the World Wide Web. The University of Minnesota eventually re-licensed its Gopher software under the GNU GPL.
  • Gopher Client functionality was quickly duplicated by early Web browsers, such as Mosaic. Furthermore, the commercial friendliness of the World Wide Web, with its integration of text and graphics, made Gopher less appealing to marketing personnel.
  • Gopher has an inflexible structure when compared to the free-form HTML of the Web. With Gopher, every document has a defined format and type, and the typical user must navigate through a single server-defined menu system to get to a particular document. Graphic Designers did not like the artificial distinction between menu and fixed document in the Gopher system, and found the Web's open-ended flexibility better suited for constructing interrelated sets of documents and interactive applications.

Availability of Gopher today

As of 2008, there are approximately 125 gopher servers indexed by Veronica-2, a slow growth from 2007 when there were fewer than 100. Many of them are owned by universities in various parts of the world. Most of them are neglected and rarely updated except for the ones run by enthusiasts of the protocol. A handful of new servers are set up every year by hobbyists - 30 have been set up and added to Floodgap's list since 1999 and possibly some more that haven't been added.

Some have suggested that the bandwidth-sparing simple interface of Gopher would be a good match for mobile phones and Personal digital assistants (PDAs), but so far, Wireless Markup Language (WML)/Wireless Application Protocol (WAP), DoCoMo i-mode, XHTML Basic or other adaptations of HTML and XML, have proved more popular. The PyGopherd server, however, provides a built-in WML front-end to Gopher sites served with it.

Gopher support in Web browsers

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. Internet Explorer for Mac (only on PowerPC architecture and in End-of-life) still supports Gopher. Internet Explorer is hard coded to work on port 70.

Other browsers, including AOL and Mozilla (deprecated), still support the protocol, but incompletely—the most obvious deficiency is that they cannot display the informational text found on many Gopher menus.

Mozilla Firefox has full Gopher support as of release 1.5, and partial support in previous versions. The SeaMonkey Internet suite, successor of the Mozilla all-in-one suite, also supports Gopher fully, as does Camino, a browser based on Mozilla's engine. Such Mozilla-based browsers are able to display embedded images from a gopher server on an HTTP-based HTML document and follow download links to a gopher server. However, it has been announced that support for the Gopher protocol will be removed by default in the Mozilla 2 platform that Firefox 4.0 will use.

Konqueror needs a plugin to be installed for full Gopher support, such as kio_gopher

The most extensive Gopher support is offered in Lynx, a text-based browser, while the Safari and Opera web browsers do not support Gopher at all (though Opera 9.0 includes a proxy capability). ELinks has experimental Gopher support (as a compile-time option).

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, MacOS 7x, MVS, NeXT, OS/2 Warp, most UNIX-like operating systems, VMS, Windows 3x, and Windows 9x. [] 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 Port 70.

Example Gopher Web Search:

gopher://gopher.floodgap.com/7/v2/vs

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 that converts Gopher menus into HTML. One such server is at Floodgap.com By default any Squid cache proxy server will act as a Gopher to HTTP gateway.

Some Gopher servers, such as GN and PyGopherd, also have built-in Gopher to HTTP interfaces.

Gopher characteristics

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.


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 INFORMATIONAL RFC 1436 IANA has assigned TCP port 70 to the Gopher protocol.

The gopher protocol is extremely simple in its conception, making it possible to browse without using a client. A standard gopher [] session may therefore appear as follows:

telnet quux.org 70 Trying 64.85.160.193... Connected to quux.org. Escape character is '^]'. /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 Connection closed by foreign host.

Here, the client has established a TCP connection with the server, on Port 70, the standard gopher port. The client then it sends "/Reference" followed by a carriage return followed by a line feed (a "CR + LF" sequence). This is the item selector, which identifies the document to be retrieved. If the item selector were an empty line, the default directory will 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 its self. 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 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 the gopherspace by following the links. All lines in a directory listing are ended with "CR + LF" and consist of five fields: Type (see below), User_Name (i.e. the text to display), Selector (i.e. the file name), Host and Port. The Type and User_Name fields are joined without a space; the other fields are separated by tabs.

Gopher Types

File-types are described in gopher menus by a single letter or number. The original protocol defines 14 types, with others being added by the community. Older clients may not handle new file types, such as d for PDF, which is why many authors use the generic 9 for all binary files, 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 the file to simulate an HTTP client 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 "h", the description is arbitrary, the item selector is "URL:http://gopher.quux.org", and the domain and port are that of the originating Gopher server. For clients that do not support URL links, the server creates an HTML redirection page.

Related technology

The main Gopher search engine is Veronica. Veronica offers a keyword search of most Gopher server menu titles in the gopher web. A Veronica search produces a menu of Gopher items, each of which is a direct pointer to a Gopher data source. Currently, there is only one Veronica-2 server.

[] is a 3D variant of the original Gopher system.

Gopher server software

See also

  • Veronica - the search engine system for the Gopher protocol, an acronym for "Very Easy Rodent-Oriented Net-wide Index to Computer Archives".
  • Jugtail - an alternative search engine system for the Gopher protocol. Jugtail was formerly known as Jughead.
  • [] - early proposed extensions to the Gopher protocol
  • Super Dimension Fortress - a non-profit organization which provides free Gopher hosting
  • Phlog - The gopher version of a weblog
  • Wide area information server - a search engine whose popularity was contemporary with Gopher

References and footnotes

External links

Standards

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