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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Key Applications and Application Protocols
           9  TCP/IP File and Message Transfer Applications and Protocols (FTP, TFTP, Electronic Mail, USENET, HTTP/WWW, Gopher)

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HTTP State Management Using "Cookies"
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TCP/IP Interactive and Remote Application Protocols
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Gopher Protocol (Gopher)
(Page 2 of 4)

Gopher Client/Server Operation

Typical use of Gopher begins with a user on a client machine creating a TCP connection to a Gopher server using well-known TCP port number 70. After the connection is established, the server waits for the client to request a particular resource by sending the server a piece of text called a selector string. Often, when a user first accesses a server, he or she does not know what resource to request, so a null (empty) selector string is sent. This causes the server to send back to the client a list of the resources available at the top (root) directory of the server’s file system tree.

Directory Listing Structure

A directory list sent by the server consists of a set of lines, each of which describes one available resource in that directory. Each line contains the following elements, each of which is separated by a “<Tab>” character:

  • Type Character and Resource Name: The first character of the line tells the client software what sort of resource the line represents. The most common type characters are “0” for a file, “1” for a subdirectory and “7” for a search service. The rest of the characters up to the first “<Tab>” contain the name of the resource to be presented to the user.

  • Selector String: The string of text to be sent to the server to retrieve this resource.

  • Server Name: The name of the server where the resource is located.

  • Server Port Number: The port number to be used for accessing this resource’s server; normally 70.

Each line ends with a “<CR><LF>” character sequence consistent with the Telnet Network Virtual Terminal (NVT) specification. Upon sending the directory listing (or any other response) the connection between the client and server is closed.


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HTTP State Management Using "Cookies"
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TCP/IP Interactive and Remote Application Protocols
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Version 3.0 - Version Date: September 20, 2005

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