Gopher (protocol)
From Wikipedia, the free encyclopedia
| The five layer TCP/IP model |
| 5. Application layer |
|
DHCP • DNS • FTP • HTTP • IMAP4 • IRC • NNTP • XMPP • MIME • POP3 • SIP • SMTP • SNMP • SSH • TELNET • BGP • RPC • RTP • RTCP • TLS/SSL • SDP • SOAP • L2TP • PPTP • … |
| 4. Transport layer |
| 3. Network layer |
| 2. Data link layer |
|
ATM • DTM • Ethernet • FDDI • Frame Relay • GPRS • PPP • ARP • RARP • … |
| 1. Physical layer |
|
Ethernet physical layer • ISDN • Modems • PLC • SONET/SDH • G.709 • Wi-Fi • … |
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, with 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. Some consider it to be the superior protocol for storing and searching large repositories of information.
Contents |
[edit] 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:
- Users instruct it to "go for" information
- It does so through a web of menu items analogous to gopher holes
- 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 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 CSO 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.
[edit] Stagnation
The World Wide Web was in its infancy in 1991, and Gopher services quickly became established. However, by the late 1990s, Gopher had ceased expanding. Insofar as information management is concerned, the shift in user base from Gopher to the web can be seen simply as a preference progression from text-based to graphical interfaces. Several other factors contributed to the acceleration of Gopher's stagnation:
- In February of 1993, the University of Minnesota announced that it would charge licensing fees for the use of its implementation of the Gopher server.[3] As a consequence of this some users suspected that a licensing fee would also be charged for independent implementations.[4][5] In contrast, no such limitation has yet to be imposed on the World Wide Web. The University of Minnesota eventually re-licensed its Gopher software under the GNU GPL.[6]
- Gopher Client functionality was quickly duplicated by early Web browsers, such as Mosaic. Furthermore, the greater flexibility of the Web's HTML, and particularly the commercial appeal of its integration of text and graphics, encouraged the migration of content from Gopher to the World Wide Web.[citation needed]
- 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.
[edit] Availability of Gopher today
As of 2007, there are fewer than 100 gopher servers on the internet.[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 - 25 have been set up and added to Floodgap's list since 1999 and possibly some more that haven't been added. Today Gopher exists as an almost forgotten corner of the internet - one can publish email addresses in plaintext without having to worry about spam, and publish large amounts of data without the risk of the server's bandwidth becoming saturated, while at the same time people do still browse the gopher servers regularly.
Some have suggested that the bandwidth-sparing simple interface of Gopher would be a good match for mobile phones and Personal digital assistants (PDAs),[8] but so far, the 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.
[edit] 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.[9] In Internet Explorer 7, Gopher support was removed on the WinINET level.[10] Internet Explorer for Mac (only on PowerPC architecture and in End-of-life) still supports Gopher.
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 Web browser does not support Gopher at all while Opera requires the use of a proxy such as Squid.
[edit] UNIX Gopher client
A purpose-made open source gopher client for gopher exists. This is simply called gopher and is available in most Linux software repositories and source packages are available on the internet as well as some gopher servers. This client has the ability to fetch additional details about the files such as their size and their owner.
[edit] Gopher to HTTP gateways
Users of Web browsers that have incomplete or no support for Gopher[11] 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, like PyGopherd, also have built-in Gopher to HTTP interfaces.
[edit] Gopher characteristics
A Gopher system consists of a series of hierarchical menus. The choice of menu items and titles is set 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.
[edit] Technical details
[edit] Protocol
The Gopher protocol is documented in RFC 1436. It is traditionally served on TCP port 70.
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:
- item type character, which is usually one of the following:
- 0 = plain text file
- 1 = directory
- 3 = error
- 5 = ZIP archive
- 7 = search server (returns a directory)
- 8 = telnet connection
- 9 = binary file
- h = html file
- i = informational text
- I = image file
- description text
- item selector (typically a file-system pathname)
- domain name of the server on which the item resides
- port number of that server
[edit] 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 [12] 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.
[edit] 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.
GopherVR is a 3D variant of the original Gopher system.
[edit] See also
- Veronica - the search engine system for the Gopher protocol, an acronym for "Very Easy Rodent-Oriented Net-wide Index to Computer Archives".
- Jughead - an alternative search engine system for the Gopher protocol.
- Gopher+ - extensions to the Gopher protocol
- HyTelnet - a similar mechanism for unifying Telnet-based interfaces
- Super Dimension Fortress - a non-profit organization which provides free Gopher access
- Phlog - The gopher version of a weblog
[edit] References and footnotes
- ^ Google Groups archive of bit.listserv.cwis-l discussion
- ^ Google Groups archive of comp.infosystems.gopher discussion
- ^ http://www.funet.fi/pub/vms/networking/gopher/gopher-software-licensing-policy.ancient
- ^ http://groups.google.com/groups?selm=1mj6cb$6gm@pith.uoregon.edu
- ^ http://groups.google.com/groups?AMITselm=36e4c2f1.10244576@nntp.best.ix.netcom.com
- ^ ftp://boombox.micro.umn.edu/pub/gopher/gopher-software-licensing-policy.new
- ^ Kaiser, Cameron (2007-03-19). Down the Gopher Hole. TidBITS. Retrieved on March 23, 2007.
- ^ Wired News: Gopher: Underground Technology
- ^ Microsoft Security Bulletin MS02-047. Microsoft (2003-02-28). Retrieved on March 23, 2007.
- ^ Release Notes for Internet Explorer 7. Microsoft (2006). Retrieved on March 23, 2007.
- ^ To determine whether a Web browser supports Gopher, compare the display of this gopher menu with the same menu produced by a Gopher to HTML gateway in the browser.
- ^ http://gopher.quux.org/Archives/Mailing%20Lists/gopher/gopher.2002-02|/MBOX-MESSAGE/34
[edit] External links
- Gopher Jewels 2 (gopher link)
- The Gopher Project
- The state of Gopher support for common Web browsers
- List of new Gopher servers since 1999 (gopher link)
- List of Gopher servers
- Gopher Clients
