RFC du protocole NNTP : specification
2. The NNTP Specification
2.1. Overview
The news server specified by this document uses a stream connection
(such as TCP) and SMTP-like commands and responses. It is designed
to accept connections from hosts, and to provide a simple interface
to the news database.
This server is only an interface between programs and the news
databases. It does not perform any user interaction or presentation-
level functions. These "user-friendly" functions are better left to
the client programs, which have a better understanding of the
environment in which they are operating.
When used via Internet TCP, the contact port assigned for this
service is 119.
2.2. Character Codes
Commands and replies are composed of characters from the ASCII
character set. When the transport service provides an 8-bit byte
(octet) transmission channel, each 7-bit character is transmitted
right justified in an octet with the high order bit cleared to zero.
2.3. Commands
Commands consist of a command word, which in some cases may be
followed by a parameter. Commands with parameters must separate the
parameters from each other and from the command by one or more space
or tab characters. Command lines must be complete with all required
parameters, and may not contain more than one command.
Commands and command parameters are not case sensitive. That is, a
command or parameter word may be upper case, lower case, or any
mixture of upper and lower case.
Each command line must be terminated by a CR-LF (Carriage Return -
Line Feed) pair.
Command lines shall not exceed 512 characters in length, counting all
characters including spaces, separators, punctuation, and the
trailing CR-LF (thus there are 510 characters maximum allowed for the
command and its parameters). There is no provision for continuation
command lines.
2.4. Responses
Responses are of two kinds, textual and status.
2.4.1. Text Responses
Text is sent only after a numeric status response line has been sent
that indicates that text will follow. Text is sent as a series of
successive lines of textual matter, each terminated with CR-LF pair.
A single line containing only a period (.) is sent to indicate the
end of the text (i.e., the server will send a CR-LF pair at the end
of the last line of text, a period, and another CR-LF pair).
If the text contained a period as the first character of the text
line in the original, that first period is doubled. Therefore, the
client must examine the first character of each line received, and
for those beginning with a period, determine either that this is the
end of the text or whether to collapse the doubled period to a single
one.
The intention is that text messages will usually be displayed on the
user's terminal whereas command/status responses will be interpreted
by the client program before any possible display is done.
2.4.2. Status Responses
These are status reports from the server and indicate the response to
the last command received from the client.
Status response lines begin with a 3 digit numeric code which is
sufficient to distinguish all responses. Some of these may herald
the subsequent transmission of text.
The first digit of the response broadly indicates the success,
failure, or progress of the previous command.
1xx - Informative message
2xx - Command ok
3xx - Command ok so far, send the rest of it.
4xx - Command was correct, but couldn't be performed for
some reason.
5xx - Command unimplemented, or incorrect, or a serious
program error occurred.
The next digit in the code indicates the function response category.
x0x - Connection, setup, and miscellaneous messages
x1x - Newsgroup selection
x2x - Article selection
x3x - Distribution functions
x4x - Posting
x8x - Nonstandard (private implementation) extensions
x9x - Debugging output
The exact response codes that should be expected from each command
are detailed in the description of that command. In addition, below
is listed a general set of response codes that may be received at any
time.
Certain status responses contain parameters such as numbers and
names. The number and type of such parameters is fixed for each
response code to simplify interpretation of the response.
Parameters are separated from the numeric response code and from each
other by a single space. All numeric parameters are decimal, and may
have leading zeros. All string parameters begin after the separating
space, and end before the following separating space or the CR-LF
pair at the end of the line. (String parameters may not, therefore,
contain spaces.) All text, if any, in the response which is not a
parameter of the response must follow and be separated from the last
parameter by a space. Also, note that the text following a response
number may vary in different implementations of the server. The
3-digit numeric code should be used to determine what response was
sent.
Response codes not specified in this standard may be used for any
installation-specific additional commands also not specified. These
should be chosen to fit the pattern of x8x specified above. (Note
that debugging is provided for explicitly in the x9x response codes.)
The use of unspecified response codes for standard commands is
prohibited.
We have provided a response pattern x9x for debugging. Since much
debugging output may be classed as "informative messages", we would
expect, therefore, that responses 190 through 199 would be used for
various debugging outputs. There is no requirement in this
specification for debugging output, but if such is provided over the
connected stream, it must use these response codes. If appropriate
to a specific implementation, other x9x codes may be used for
debugging. (An example might be to use e.g., 290 to acknowledge a
remote debugging request.)
2.4.3. General Responses
The following is a list of general response codes that may be sent by
the NNTP server. These are not specific to any one command, but may
be returned as the result of a connection, a failure, or some unusual
condition.
In general, 1xx codes may be ignored or displayed as desired; code
200 or 201 is sent upon initial connection to the NNTP server
depending upon posting permission; code 400 will be sent when the
NNTP server discontinues service (by operator request, for example);
and 5xx codes indicate that the command could not be performed for
some unusual reason.
100 help text
190
through
199 debug output
200 server ready - posting allowed
201 server ready - no posting allowed
400 service discontinued
500 command not recognized
501 command syntax error
502 access restriction or permission denied
503 program fault - command not performed
|