REQUEST The request is sent with a first line containing the method to be applied to the object requested, the identifier of the object, and the protocol version in use, followed by further information encoded in the RFC822 header style. The format of the request is: Request = SimpleRequest | FullRequest SimpleRequest = GET <uri> CrLf FullRequest = Method UR ProtocolVersion CrLf [*<HTRQ Header>] [<CrLf> <data>] <Method> = <InitialAlpha> ProtocolVersion = HTTP/V1.0 uri = <as defined in URL spec> <HTRQ Header> = <Fieldname> : <Value> <CrLf> <data> = MIME-conforming-message
The URI is the Uniform Resource Locator (URL) as defined in the specification, or may be (when it is defined) a Uniform Resource Name (URN) when a specification for this is settled, for servers which support URN resolution.
Unless the server is being used as a gateway, a partial URL shall be given with the assumptions of the protocol (HTTP:) and server (the server) being obvious.
The URI should be encoded using the escaping scheme described in the URL specification to a level such that (at least) spaces and control characters (decimal 0-31 and 128-159) do not appear unesacaped.
Note. The rest of an HTTP url after the host name and optional port number is completely opaque to the client: The client may make no deductions about the object from its URL.
The Protocol/Version field defines the format of the rest of the request.. At the moment only HTRQ is defined .
If the protocol version is not specified, the server assumes that the browser uses HTTP version 0.9.
Uniform Resource Identifier
This is a string identifying the object. It contains no blanks. It may be a Uniform Resource Locator [ URL ] defining the address of an object as described in RFCxxxx, or it may be a representation of the name of an object (URN, Universal Resource Name) where that object has been registered in some name space. At the time of writing, no suitable naming system exists, but this protocol will accept such names so long as they are distinguishable from the existing URL name spaces.
Method field indicates the method to be performed on the object identified by the URL. More details are with the list of method names below .
These are RFC822 format headers with special field names given in the list below , as well as any other HTTP object headers or MIME headers.
The content of an object is sent (depending on the method) with the request and/or the reply.
The Method field in HTTP indicates the method to be performed on the object identified by the URL. The method GET below is always supported, The list of other methods acceptable by the object are returned in response to either of these two requests.
This list may be extended from time to time by a process of registration with the design authority. Method names are case sensitive. Currently specified methods are as follows:
RESPONSE The response from the server shall start with the following syntax (See also: note on client tolerance ): <status line> ::= <http version> <status code> <reason line> <CrLf> <http version> ::= 3*<digit> <status code> ::= 3*<digit> <digit> ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 <reason line> ::= * <printable> <http version> identifies the HyperText Transfer Protocol version being used by the server. For the version described by this document version it is "HTTP/1.0" (without the quotes). < status code > gives the coded results of the attempt to understand and satisfy the request. A three digit ASCII decimal number. <reason string> gives an explanation for a human reader, except where noted for particular status codes. Fields on the status line are delimited by a single blank (parsers should accept any amount of white space). The possible values of the status code are listed below . Response headers The headers on returned objects those RFC822 format headers listed as object headers , as well as any MIME conforming headers, notably the Content-Type field. Note that this specification doesnot define any headers particular to the response which are not also appropriate to any transmission of an object with a request. Response data Additional information may follow, in the format of a MIME message body. The significance of the data depends on the status code. The Content-Type used for the data may be any Content-Type which the client has expressed his ability to accept, or text/plain, or text/html. That is, one can always assume that the client can handle text/plain and text/html. Status codes The values of the numeric status code to HTTP requests are as follows. The data sections of messages Error, Forward and redirection responses may be used to contain human-readable diagnostic information. SUCCESS 2XX These codes indicate success. The body section if present is the object returned by the request. It is a MIME format object. It is in MIME format, and may only be in text/plain, text/html or one fo the formats specified as acceptable in the request. OK 200 The request was fulfilled. CREATED 201 Following a POST command, this indicates success, but the textual part of the response line indicates the URI by which the newly created document should be known. Accepted 202 The request has been accepted for processing, but the processing has not been completed. The request may or may not eventually be acted upon, as it may be disallowed when processing actually takes place. there is no facility for status returns from asynchronous operations such as this. Partial Information 203 When received in the response to a GET command, this indicates that the returned metainformation is not a definitive set of the object from a server with a copy of the object, but is from a private overlaid web. This may include annotation information about the object, for example ERROR 4XX, 5XX The 4xx codes are intended for cases in which the client seems to have erred, and the 5xx codes for the cases in which the server is aware that the server has erred. It is impossible to distinguish these cases in general, so the difference is only informational. The body section may contain a document describing the error in human readable form. The document is in MIME format, and may only be in text/plain, text/html or one for the formats specified as acceptable in the request. Bad request 400 The request had bad syntax or was inherently impossible to be satisfied. Unauthorized 401 The parameter to this message gives a specification of authorization schemes which are acceptable. The client should retry the request with a suitable Authorization header. PaymentRequired 402 The parameter to this message gives a specification of charging schemes acceptable. The client may retry the request with a suitable ChargeTo header. Forbidden 403 The request is for something forbidden. Authorization will not help. Not found 404 The server has not found anything matching the URI given Internal Error 500 The server encountered an unexpected condition which prevented it from fulfilling the request. Not implemented 501 The server does not support the facility required. REDIRECTION 3XX The codes in this section indicate action to be taken (normally automatically) by the client in order to fulfill the request. Moved 301 The data requested has been assigned a new URI, the change is permanent. (N.B. this is an optimisation, which must, pragmatically, be included in this definition. Browsers with link editing capability should automatically relink to the new reference, where possible) The response contains one or more header lines of the form URI: <url> String CrLf Which specify alternative addresses for the object in question. The String is an optional comment field. If the response is to indicate a set of variants which each correspond to the requested URI, then the multipart/alternative wrapping may be used to distinguish different sets Found 302 The data requested actually resides under a different URL, however, the redirection may be altered on occasion (when making links to these kinds of document, the browser should default to using the Udi of the redirection document, but have the option of linking to the final document) as for "Forward". The response format is the same as for Moved . Method 303 Method: <method> <url> body-section Like the found response, this suggests that the client go try another network address. In this case, a different method may be used too, rather than GET. The body-section contains the parameters to be used for the method. This allows a document to be a pointer to a complex query operation.