Return codes for proxy and HTTP server requests
The return codes indicate the status of requests made on the user behalf
when the user tries to access a URL. The codes that are most useful during
the log analysis are:
200 -- OK (file was delivered to the user)
304 -- cached (the proxy has a file in the cache)
403 -- forbidden. File was blocked either by Smartfilter
(on our side) or by web server on the target side.
404 -- "file not found"
All-in all several dozen HTTP server return codes have been defined and
each uniquely describes a different condition. The codes are divided into
four categories. Each category reserves a range of 100 possible values and
defines a broad class of possible conditions:
100-199 (informational codes). Pretty rare class of
codes. They basically provide information
about the request or the servers involved.
200-299 ("success" codes). Though 200 is the most common
of these, several others exist. For example 204 is used to indicate
that the requested file is empty (no content), 202 that some request
from the user was accepted.
300-399 (redirects). This ranges includes code 304, which
indicates that the file requested has been cached and does not need
to be downloaded again.
400-499 (client errors). A client (browser) may, for example,
request a page from the server that doesn't exist. The ultimate cause
of such an error may be a mistyped link, but the errors still referred
to as a client error. Other 400 level errors include code 403 ("forbidden").
500-599 (server errors). These errors indicate that there
is an internal server error or a configuration problem that is preventing
the server from properly responding to the request. This type of error
is most often encountered in Web sites that are considerably more complex
than static HTML. Problems retrieving information from a database or
interpreting Java code might be behind server errors.
Here's a fairly complete list that you might want to print for future
reference.
200 Series:
200 - OK - Successful transmission. This is not an error
code, this is acually a success code. The file you requested was
found, here it is. The length of file transmitted is recoded
in the next field.
201 - Created - The request has been fulfilled and resulted
in a new resource being created. The newly created resource can
be referenced by the URL(s) returned in the URL-header field of
the response, with the most specific URL for the resource given
by a Location header field.
202 - Accepted - The request has
been accepted for processing, but the processing has not yet completed.
203 - Non-Authoritative Information - The returned META information
in the Entity-Header is not the definitive set as available from
the origin server, but is gathered from a local or third-party copy.
204 - No Content - The server has fulfilled the request,
but there is no new information to send back.
206 - Partial Content - you requested a range of bytes in the
file, and here they are. This is new in HTTP/1.1
300 Series:
300 - Multiple Choices - The requested source is available at
one or more locations and a preferred location could not be determined
via content negotiation.
301 - Moved Permanently - The requested resource has been assigned
a new permanent URL and any future references to this resource should
be done using one of the returned URLs.
302 - Moved Temporarily - The requested resource resides temporarily
under a new URL. Redirection to a new URL. The original page has
moved. This is not an error; most browsers invisibly fetch the new
page upon seeing this result.
303 - See Other - The requested resource resides under a different
URL and should be accessed using a Get method on that resource.
304 - Not Modified - If the client has performed a conditional
GET request and access is allowed, but the document has not been
modified since the date and time specified in the
If-Modified-Since
field, the server responds with this status code and does not send
an Entity-Body to the client. Use local copy. This means that the
copy of the file on the web server is not newer than the copy which
your web browser or proxy server has cached locally, so there's
no point in sending the file again. This is not an error. The file
hasn't changed since the last time you asked for it, so I'm not
going to send it again.
400 Series:
400 - Bad Request - The request could not be understood by the
server due to it having a malformed syntax. Bad request was made
by the client.
401 - Unauthorized - The request requires user authentication.
The response must include a WWW-Authenticate header field containing
a challenge applicable to the requested source. The user asked for
a document but did not provide a valid username or password.
402 - Payment Required - This code is not currently supported,
but is reserved for future use.
403 - Forbidden - The server understood the request but
is refusing to perform the request because of an unspecified reason.
Access is explicitly denied to this document. (This might happen
because the web server doesn't have read permission for the file
you're requesting.) The server refuses to send you this file. Maybe
permission has been explicitly turned off.
404 - Not Found - The server has not found anything matching
the requested URL. This file doesn't exist. That error often can
come from a mistyped URL or from URL that is no longer valid (for
example the site seized to exist). Sometimes this code is sent if
the server has been told to protect the document by telling unauthorized
people that it doesn't exist.
405 - Method Not Allowed - The method specified in the request
line is not allowed for the resource identified by the request URL.
406 - None Acceptable - The server has found a resource matching
the request URL, but not one that satisfies the conditions identified
by the Accept and Accept-Encoding request headers.
407 - Proxy Authentication Required - This code is reserved
for future use. It is similar to 401 (Unauthorized) but indicates
that the client must first authenticate itself with a proxy. HTTP/1.0
does not provide a means for proxy authentication.
408 - Request Timeout - The client did not produce a
request within the time the server was prepared to wait.
409 - Conflict - The request could not be completed due to a
conflict with the current state of the resource.
410 - Gone - The requested resource is no longer available at
the server and no forwarding address is known.
411 - Authorization Refused - The request credentials provided
by the client were rejected by the server or insufficient to grant
authorization to access the resource.
412 - Precondition Failed
413 - Request Entity Too Large
414 - Request URI Too Large
415 - Unsupported Media Type
500 Series:
500 - Internal Server Error - The server encountered an unexpected
condition that prevented it from filling the request. Something
went wrong with the web server and it couldn't give you a meaningful
response. There is usually nothing that can be done from the browser
end to fix this error; the server administrator will probably need
to check the server's error log to see what happened. This is often
the error message for a CGI script which has not been properly coded.
501 - Method Not Implemented - The server does not support the
functionality required to fulfill the request. Application method
(either GET or POST) is not implemented.
502 - Bad Gateway - The server received an invalid response
from the gateway or upstream server it accessed in attempting to
fulfill the request.
503 - Service Temporarily Unavailable - The server is currently
unable to handle the request due to a temporary overloading or maintenance
of the server. Server is out of resources.
504 - Gateway Timeout - The server did not receive a timely
response from the gateway or upstream server it accessed in attempting
to complete the request.
505 - HTTP Version Not Supported
8181 - Certificate has expired (secure server only).
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Last modified:
September 13, 2011