Gopher ( ) is a communication 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 Hypertext Transfer Protocol (HTTP). The Gopher ecosystem is often regarded as the effective predecessor of the World Wide Web.
Contents
Usage
The Gopher 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.
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
The 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.
Extensibility of the file system metaphor; allowing addition of searches for example.
Gopher combines document hierarchies with collections of services, including WAIS, the Archie and Veronica search engines, and gateways to other information systems such as File Transfer Protocol (FTP) and Usenet.
The general interest in campus-wide information systems (CWISs) 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, including technical design, social factors, and project governance decisions:
The Gopher project did not embrace the open collaboration model. 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. In contrast, CERN released the World Wide Web software into the public domain in April 1993.
The success of the NCSA Mosaic browser became strongly associated with the Web, with Gopher support seen as a secondary feature.
Gopher menus are separate from the documents they point to, and often organised in a hierarchy. This contrasts with the free-form HyperText Markup Language (HTML) of the Web, which mixes content and links in the same document, and encourages non-hierarchical cross-references.
In September 2000, the University of Minnesota re-licensed its Gopher software under the GNU General Public License.
Gopher remains in active use by its enthusiasts, and there have been attempts to revive Gopher on modern platforms and mobile devices. One attempt is The Overbite Project, which hosts various browser extensions and modern clients.
Server census
As of 2012, 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.
Technical details
The conceptualization of knowledge in "Gopher space" or a "cloud" as specific information in a particular file, and the prominence of the FTP, influenced the technology and the resulting functionality of Gopher.
Gopher characteristics
Gopher is designed to function and to appear 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 can be done with data files on a CD-ROM, can be done 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. Internet Assigned Numbers Authority (IANA) has assigned Transmission Control Protocol (TCP) port 70 to the Gopher protocol. The protocol is simple to negotiate, making it possible to browse without using a client.
First, the client establishes 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 closes, the server should send a full-stop (i.e., a period character) on a line by itself. However, not all servers conform to this part of the protocol and the server may close a connection without returning a final full-stop. The main type of reply from the server is a text or binary resource. Alternatively, the resource can be a menu: a form of structured text resource providing references to other resources.
Because of the simplicity of the Gopher protocol, tools such as netcat make it possible to download Gopher content easily from a command line:
The protocol is also supported by cURL since 7.21.2-DEV, which was released in 2010.
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.
Source code of a menu
Gopher menu items are defined by lines of tab-separated values in a text file. This file is sometimes called a gophermap. As the source code to a gopher menu, a gophermap is roughly analogous to an HTML file for a web page. Each tab-separated line (called a selector line) gives the client software a description of the menu item: what it is, what it is called, and where it leads to. The client displays the menu items in the order that they appear in the gophermap.
The first character in a selector line indicates the item type, which tells the client what kind of file or protocol the menu item points to. This helps the client decide what to do with it. Gopher's item types are a more basic precursor to the media type system used by the Web and email attachments.
The item type is followed by the user display string (a description or label that represents the item in the menu); the selector (a path or other string for the resource on the server); the hostname (the domain name or IP address of the server), and the network port.
All lines in a gopher menu are terminated by "CR + LF".
Example of a selector line in a menu source: The following selector line generates a link to the "/home" directory at the subdomain gopher.floodgap.com, on port 70. The item type of 1 indicates that the linked resource is a Gopher menu itself. The string "Floodgap Home" is what the client will show to the user when visiting the example menu.
1Floodgap Home /home gopher.floodgap.com 70
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. The later gopher+ specification defined an additional 3 types. A one-character code indicates what kind of content the client should expect. Item type 3 is an error code for exception handling. Gopher client authors improvised item types h (HTML), i (informational message), and s (sound file) 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.
Gopher+
Gopher+ is a forward compatible enhancement to the Gopher protocol. Gopher+ works by sending metadata between the client and the server. The enhancement was never widely adopted by Gopher servers.
The client sends a tab followed by a +. A Gopher+ server will respond with a status line followed by the content the client requested. An item is marked as supporting Gopher+ in the Gopher directory listing by a tab + after the port (this is the case of some of the items in the example above).
Other features of Gopher+ include:
Item attributes, which can include the items
Administrator
Last date of modification
Different views of the file, like PostScript or plain text, or different languages
Abstract, or description of the item
Interactive queries
Client software
Gopher clients
These are clients, libraries, and utilities primarily designed to access gopher resources.
Other clients
Clients like web browsers, libraries, and utilities primarily designed to access World Wide Web resources, but which maintain(ed) gopher support.
Browse, a browser for RISC OS
Camino, versions 1.0 to 2.1.2, always uses port 70.
Classilla, versions 9.0 to 9.3.4b1 as of March 2021, hardcoded to port 70 from 9.0 to 9.2; whitelisted ports from 9.2.1
cURL, a command line client for accessing URLs for various protocols
Dillo+
Dooble
Edbrowse, a line-oriented editor and browser with an interface like that of ed (text editor)
ELinks, versions 0.10.0 to 0.12pre6 as of October 2012, unmaintained browser with gopher build option. Fork felinks offers support as a build option
Falkon, with plug-in only, requires Falkon ≥ 3.1.0 with both the KDE Frameworks Integration extension (shipped with Falkon ≥ 3.1.0) enabled and the (separate) kio_gopher plug-in ≥ 0.1.99 (first release for KDE Frameworks 5) installed
Mozilla Firefox versions 0.1 to 3.6, built-in support dropped from Firefox 4.0 onwards; can be added back by installing one of the extensions by the Overbite Project
Galeon version 2.0.7
Epiphany, until version 2.26.3, disabled with switch to WebKit
Google Chrome, with extension only, Burrow extension
Internet Explorer, dropped with version 6: Support removed by MS02-047 from IE 6 SP1 can be re-enabled in the Windows Registry. Always uses port 70. 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.
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.