Network Working Group                                         P. Hoffman
Request for Comments: 4266                                VPN Consortium
Obsoletes: 1738                                            November 2005
Category: Standards Track


                        The gopher URI Scheme

Status of This Memo

  This document specifies an Internet standards track protocol for the
  Internet community, and requests discussion and suggestions for
  improvements.  Please refer to the current edition of the "Internet
  Official Protocol Standards" (STD 1) for the standardization state
  and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

  Copyright (C) The Internet Society (2005).

Abstract

  This document specifies the gopher Uniform Resource Identifier (URI)
  scheme that was originally specified in RFC 1738.  The purpose of
  this document is to allow RFC 1738 to be made obsolete while keeping
  the information about the scheme on standards track.

1.  Introduction

  URIs were previously defined in RFC 2396 [RFC2396], which was updated
  by RFC 3986 [RFC3986].  Those documents also specify how to define
  schemes for URIs.

  The first definition for many URI schemes appeared in RFC 1738
  [RFC1738].  Because that document has been made obsolete, this
  document copies the gopher URI scheme from it to allow that material
  to remain on standards track.

2.  Scheme Definition

  The gopher URL scheme is used to designate Internet resources
  accessible using the Gopher protocol.

  The base Gopher protocol is described in RFC 1436 [RFC1436] and
  supports items and collections of items (directories).  The Gopher+
  protocol is a set of upward-compatible extensions to the base Gopher
  protocol and is described in [Gopher+].  Gopher+ supports associating




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  arbitrary sets of attributes and alternate data representations with
  Gopher items.  Gopher URLs accommodate both Gopher and Gopher+ items
  and item attributes.

  Historical note: The Gopher protocol was widely implemented in the
  early 1990s, but few Gopher servers are in use today.

2.1.  Gopher URL Syntax

  A Gopher URL takes the form:

     gopher://<host>:<port>/<gopher-path>

  where <gopher-path> is one of:

     <gophertype><selector>
     <gophertype><selector>%09<search>
     <gophertype><selector>%09<search>%09<gopher+_string>

  If :<port> is omitted, the port defaults to 70. <gophertype> is a
  single-character field to denote the Gopher type of the resource to
  which the URL refers.  The entire <gopher-path> may also be empty, in
  which case the delimiting "/" is also optional and the <gophertype>
  defaults to "1".

  <selector> is the Gopher selector string.  In the Gopher protocol,
  Gopher selector strings are a sequence of octets that may contain any
  octets except 09 hexadecimal (US-ASCII HT or tab), 0A hexadecimal
  (US-ASCII character LF), and 0D (US-ASCII character CR).

  Gopher clients specify which item to retrieve by sending the Gopher
  selector string to a Gopher server.

  Within the <gopher-path>, no characters are reserved.

  Note that some Gopher <selector> strings begin with a copy of the
  <gophertype> character, in which case that character will occur twice
  consecutively.  The Gopher selector string may be an empty string;
  this is how Gopher clients refer to the top-level directory on a
  Gopher server.

2.2.  Specifying URLs for Gopher Search Engines

  If the URL refers to a search to be submitted to a Gopher search
  engine, the selector is followed by an encoded tab (%09) and the
  search string.  To submit a search to a Gopher search engine, the
  Gopher client sends the <selector> string (after decoding), a tab,
  and the search string to the Gopher server.



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2.3.  URL Syntax for Gopher+ Items

  Historical note: Gopher+ was uncommon even when Gopher was popular.

  URLs for Gopher+ items have a second encoded tab (%09) and a Gopher+
  string.  Note that in this case, the %09<search> string must be
  supplied, although the <search> element may be the empty string.

  The <gopher+_string> is used to represent information required for
  retrieval of the Gopher+ item.  Gopher+ items may have alternate
  views and arbitrary sets of attributes, and they may have electronic
  forms associated with them.

  To retrieve the data associated with a Gopher+ URL, a client will
  connect to the server and send the Gopher selector, followed by a tab
  and the search string (which may be empty), followed by a tab and the
  Gopher+ commands.

2.4.  Default Gopher+ Data Representation

  When a Gopher server returns a directory listing to a client, the
  Gopher+ items are tagged with either a "+" (denoting Gopher+ items)
  or a "?" (denoting Gopher+ items that have a +ASK form associated
  with them).  A Gopher URL with a Gopher+ string consisting of only a
  "+" refers to the default view (data representation) of the item, and
  a Gopher+ string containing only a "?" refers to an item with a
  Gopher electronic form associated with it.

2.5.  Gopher+ Items with Electronic Forms

  Gopher+ items that have a +ASK associated with them (i.e., Gopher+
  items tagged with a "?") require the client to fetch the item's +ASK
  attribute to get the form definition, and then ask the user to fill
  out the form and return the user's responses along with the selector
  string to retrieve the item.  Gopher+ clients know how to do this but
  depend on the "?" tag in the Gopher+ item description to know when to
  handle this case.  The "?" is used in the Gopher+ string to be
  consistent with Gopher+ protocol's use of this symbol.

2.6.  Gopher+ Item Attribute Collections

  To refer to the Gopher+ attributes of an item, the Gopher URL's
  Gopher+ string consists of "!" or "$". "!" refers to all of a Gopher+
  item's attributes. "$" refers to all the item attributes for all
  items in a Gopher directory.






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2.7.  Referring to Specific Gopher+ Attributes

  To refer to specific attributes, the URL's gopher+_string is
  "!<attribute_name>" or "$<attribute_name>".  For example, to refer to
  the attribute containing the abstract of an item, the gopher+_string
  would be "!+ABSTRACT".

  To refer to several attributes, the gopher+_string consists of the
  attribute names separated by coded spaces.  For example,
  "!+ABSTRACT% 20+SMELL" refers to the +ABSTRACT and +SMELL attributes
  of an item.

2.8.  URL Syntax for Gopher+ Alternate Views

  Gopher+ allows for optional alternate data representations (alternate
  views) of items.  To retrieve a Gopher+ alternate view, a Gopher+
  client sends the appropriate view and language identifier (found in
  the item's +VIEW attribute).  To refer to a specific Gopher+
  alternate view, the URL's Gopher+ string would be in the form:

     +<view_name>%20<language_name>

  For example, a Gopher+ string of "+application/postscript%20Es_ES"
  refers to the Spanish language postscript alternate view of a Gopher+
  item.

2.9.  URL Syntax for Gopher+ Electronic Forms

  The gopher+_string for a URL that refers to an item referenced by a
  Gopher+ electronic form (an ASK block) filled out with specific
  values is a coded version of what the client sends to the server.
  The gopher+_string is of the form:

     +%091%0D%0A+-1%0D%0A<ask_item1_value>%0D%0A
     <ask_item2_value>%0D%0A.%0D%0A

  To retrieve this item, the Gopher client sends the following text to
  the Gopher server.

     <a_gopher_selector><tab>+<tab>1<cr><lf>
     +-1<cr><lf>
     <ask_item1_value><cr><lf>
     <ask_item2_value><cr><lf>
     .<cr><lf>







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3.  Security Considerations

  There are many security considerations for URI schemes discussed in
  [RFC3986].  The Gopher protocol uses passwords in the clear for
  authentication, and offers no privacy, both of which are considered
  extremely unsafe in current practice.

4.  Informative References

  [Gopher+]  Anklesaria, F., et al., "Gopher+: Upward compatible
             enhancements to the Internet Gopher protocol", University
             of Minnesota, July 1993, <ftp://boombox.micro.umn.edu/pub/
             gopher/gopher_protocol/Gopher+/Gopher+.txt>

  [RFC1738]  Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
             Resource Locators (URL)", RFC 1738, December 1994.

  [RFC2396]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
             Resource Identifiers (URI): Generic Syntax", RFC 2396,
             August 1998.

  [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
             Resource Identifier (URI): Generic Syntax", STD 66,
             RFC 3986, January 2005.

  [RFC1436]  Anklesaria, F., McCahill, M., Lindner, P., Johnson, D.,
             Torrey, D., and B. Albert, "The Internet Gopher Protocol
             (a distributed document search and retrieval protocol)",
             RFC 1436, March 1993.

Author's Address

  Paul Hoffman
  VPN Consortium
  127 Segre Place
  Santa Cruz, CA  95060
  US

  EMail: [email protected]












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Full Copyright Statement

  Copyright (C) The Internet Society (2005).

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Acknowledgement

  Funding for the RFC Editor function is currently provided by the
  Internet Society.







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