Request HeaderExpect
Beispiel:
Expect: 100-continue
Original Beschreibung (engl.):
The Expect request-header field is used to indicate that particular
server behaviors are required by the client.
Expect = "Expect" ":" 1#expectation
expectation = "100-continue" | expectation-extension
expectation-extension = token [ "=" ( token | quoted-string )
*expect-params ]
expect-params = ";" token [ "=" ( token | quoted-string ) ]
A server that does not understand or is unable to comply with any of
the expectation values in the Expect field of a request MUST respond
with appropriate error status. The server MUST respond with a 417
(Expectation Failed) status if any of the expectations cannot be met
or, if there are other problems with the request, some other 4xx
status.
This header field is defined with extensible syntax to allow for
future extensions. If a server receives a request containing an
Expect field that includes an expectation-extension that it does not
support, it MUST respond with a 417 (Expectation Failed) status.
Comparison of expectation values is case-insensitive for unquoted
tokens (including the 100-continue token), and is case-sensitive for
quoted-string expectation-extensions.
The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy MUST
return a 417 (Expectation Failed) status if it receives a request
with an expectation that it cannot meet. However, the Expect
request-header itself is end-to-end; it MUST be forwarded if the
request is forwarded.
Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
Expect header.
See section 8.2.3 for the use of the 100 (continue) status.
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