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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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