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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)
9 TCP/IP World Wide Web (WWW, "The Web") and the Hypertext Transfer Protocol (HTTP)
9 TCP/IP Hypertext Transfer Protocol (HTTP)
9 HTTP Messages, Message Formats, Methods and Status Codes
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HTTP Status Code Format, Status Codes and Reason Phrases
(Page 2 of 4)
Status Code Format
HTTP status codes are three digits
in length and follow a particular format where the first digit has particular
significance. Unlike FTP and the others, the second digit does not stand
for a functional grouping; the second and third digits together just
make 100 different options for each of the categories indicated by the
first digit. Thus, the general form of an HTTP status code is xyy,
where the first digit, x, is specified as given in Table 274.
Table 274: HTTP Status Code Format: First Digit Interpretation
Status
Code Format
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Meaning
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Description
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1yy
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Informational
Message
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Provides general information;
does not indicate success or failure of a request.
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2yy
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Success
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The method
was received, understood and accepted by the server.
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3yy
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Redirection
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The request did not fail outright,
but additional action is needed before it can be successfully completed.
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4yy
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Client
Error
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The request
was invalid, contained bad syntax or could not be completed for some
other reason that the server believes was the client's fault.
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5yy
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Server Error
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The request was valid but the
server was unable to complete it due to a problem of its own.
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In each of these five groups,
the code where yy is 00 is defined as a generic
status code for that group, while other two-digit combinations are more
specific responses. For example, 404 is the well-known specific
error message that means the requested resource was not found by the
server, while 400 is the less specific bad request
error. This system was set up to allow the definition of new status
codes that certain clients might not comprehend. If a client receives
a strange code, it just treats it as the equivalent of the generic response
in the appropriate category. So if a server response starts with the
code 491 and the client has no idea what this is, it just
treats it as a 400 bad request reply.
Reason Phrases
The reason phrase is a text string
that provides a more meaningful description of the error for people
who are bad at remembering what cryptic codes stand for (which would
be most of us!) The HTTP standard includes sample reason
phrases for each status code, but these can be customized by the administrators
of a server if desired. When a server returns a more detailed HTML error
message in the body of its response message, the reason phrase is often
used for the title tag in that message body.
Key Concept: Each HTTP response includes both a numeric status code and a text reason phrase, both of which indicate the disposition of the corresponding client request. The numeric code allows software programs to easily interpret the results of a request, while the text phrase provides more useful information to human users. HTTP status codes are three digits in length, with the first digit indicating the general class of the reply. |
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Version 3.0 - Version Date: September 20, 2005
© Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.
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