reasons:

      (a) A hierarchical arrangement of information is familiar to many
      users.  Hierarchical directories containing items (such as
      documents, servers, and subdirectories) are widely used in
      electronic bulletin boards and other campus-wide information
      systems. People who access a campus-wide information server will
      expect some sort of hierarchical organization to the information
      presented.





 
RFC 1436                         Gopher                       March 1993


      (b) A file-system style hierarchy can be expressed in a simple
      syntax.  The syntax used for the internet Gopher protocol is
      easily understandable, and was designed to make debugging servers
      and clients easy.  You can use Telnet to simulate an internet
      Gopher client's requests and observe the responses from a server.
      Special purpose software tools are not required.  By keeping the
      syntax of the pseudo-file system client/server protocol simple, we
      can also achieve better performance for a very common user
      activity: browsing through the directory hierarchy.

      (c) Since Gopher originated in a University setting, one of the
      goals was for departments to have the option of publishing
      information from their inexpensive desktop machines, and since
      much of the information can be presented as simple text files
      arranged in directories, a protocol modeled after a file system
      has immediate utility.  Because there can be a direct mapping from
      the file system on the user's desktop machine to the directory
      structure published via the Gopher protocol, the problem of
      writing server software for slow desktop systems is minimized.

      (d) A file system metaphor is extensible.  By giving a "type"
      attribute to items in the pseudo-file system, it is possible to
      accommodate documents other than simple text documents.  Complex
      database services can be handled as a separate type of item.  A
      file-system metaphor does not rule out search or database-style
      queries for access to documents.  A search-server type is also
      defined in this pseudo-file system.  Such servers return "virtual
      directories" or list of documents matching user specified
      criteria.

2.  The internet Gopher Model

   A detailed BNF rendering of the internet Gopher syntax is available
   in the appendix...but a close reading of the appendix may not be
   necessary to understand the internet Gopher protocol.

   In essence, the Gopher protocol consists of a client connecting to a
   server and sending the server a selector (a line of text, which may
   be empty) via a TCP connection.  The server responds with a block of
   text terminated with a period on a line by itself, and closes the
   connection.  No state is retained by the server between transactions
   with a client. The simple nature of the protocol stems from the need
   to implement servers and clients for the slow, smaller desktop
   computers (1 MB Macs and DOS machines), quickly, and efficiently.

   Below is a simple example of a client/server interaction; more
   complex interactions are dealt with later.  Assume that a "well-
   known" Gopher server (this may be duplicated, details are discussed




 
RFC 1436                         Gopher                       March 1993


   later) listens at a well known port for the campus (much like a
   domain-name server).  The only configuration information the client
   software retains is this server's name and port number (in this
   example that machine is rawBits.micro.umn.edu and the port 70). In
   the example below the F character denotes the TAB character.

 Client:          {Opens connection to rawBits.micro.umn.edu at port 70}

 Server:          {Accepts connection but says nothing}

 Client:  {Sends an empty line: Meaning "list what you have"}

 Server:          {Sends a series of lines, each ending with CR LF}
 0About internet GopherFStuff:About usFrawBits.micro.umn.eduF70
 1Around University of MinnesotaFZ,5692,AUMFunderdog.micro.umn.eduF70
 1Microcomputer News & PricesFPrices/Fpserver.bookstore.umn.eduF70
 1Courses, Schedules, CalendarsFFevents.ais.umn.eduF9120
 1Student-Staff DirectoriesFFuinfo.ais.umn.eduF70
 1Departmental PublicationsFStuff:DP:FrawBits.micro.umn.eduF70
                    {.....etc.....}
 .                  {Period on a line by itself}
                    {Server closes connection}


   The first character on each line tells whether the line describes a
   document, directory, or search service (characters '0', '1', '7';