Gopher (protocol)
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. The Gopher ecosystem is often regarded as the effective predecessor of the World Wide Web.
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 :- 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.
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 which released the WWW into the public domain in April 1993, to which CERN maintained. 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 HyperText Markup Language 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.
- Failure to follow the open systems model and bad publicity in comparison to the World Wide 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.
| Index Date | Gopher Servers | Unique Selectors | |
| 86 | 740,000 | ||
| 148 | 1,220,665 | ||
| - | |||
| 144 | - | ||
| 144 | 3,314,158 | ||
| 137 | 4,396,061 | ||
| 146 | 5,176,602 | ||
| 260 | - | ||
| 297 | 3,946,750 | ||
| 320 | - | ||
| 395 | - | ||
| 358 | 5,973,552 | ||
| 343 | 5,294,599 | ||
| 333 | 5,098,733 | ||
| 323 | 5,113,957 | ||
| 296 | 5,113,382 | ||
| 432 | 5,254,158 | ||
| 411 | 5,856,111 |
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. 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. Internet Assigned Numbers Authority has assigned Transmission Control Protocol port 70 to the Gopher protocol. The protocol is simple to negotiate, making it possible to browse without using a client.User request
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. 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.Server response
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 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:
$ echo jacks/jack.exe | nc gopher.example.org 70 > jack.exe
The protocol is also supported by cURL since 7.21.2-DEV, which was released in 2010.
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,, 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 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, 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.
Here is an example gopher session where the user requires a gopher menu :
/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
The gopher menu sent back from the server is 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.
This menu includes a text resource, multiple links to submenus and a non-standard information message, broken down to multiple lines by providing dummy values for selector, host and port.