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.
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:
The source of the name "Gopher" is claimed to be threefold:
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)[1] 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.[2]
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.
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 the acceleration of Gopher's stagnation:
As of 2007, there are fewer than 100 gopher servers indexed by Veronica-2.[7] 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[8] 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),[9] but so far, the Web-fixated market prefers Wireless Markup Language (WML)/Wireless Application Protocol (WAP), DoCoMo i-mode, XHTML Basic or other adaptations of HTML and XML. The PyGopherd server, however, provides a built-in WML front-end to Gopher sites served with it.
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.[10] In Internet Explorer 7, Gopher support was removed on the WinINET level.[11] 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 Mozilla and AOL, still support the protocol, but incompletely - the most obvious deficiency is that they cannot display the informational text found on many Gopher menus. Konqueror needs a plugin to be installed for full Gopher support, such as kio_gopher. 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, the most extensive gopher support is offered in Lynx, a text based browser.
The Safari and Opera web browsers, (although Opera 9.0 includes a proxy capability) do not support Gopher at all.
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. There are several Gopher Clients designed for 3D visualization, and even a Gopher Client MOO object. The majority of these clients are hard coded to work on Port 70.
Users of Web browsers that have incomplete or no support for Gopher[12] 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.
In characteristic, 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.
The Gopher protocol was first described in INFORMATIONAL RFC 1436. IANA has assigned TCP port 70 to the Gopher protocol.
After the client has established a TCP connection with the server, it sends a line that contains the item selector, a string that identifies the document to be retrieved. The line is ended with a carriage return followed by a line feed (a "CR + LF" sequence). An empty line will select the default directory. The server then replies with the requested item and closes the connection.
A directory consists of a sequence of lines, each of which describes an item that can be retrieved. These lines are ended with "CR + LF". They consist of five fields, separated by TAB characters:
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 [13] 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.
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.
GopherVR is a 3D variant of the original Gopher system.