问题
If a response to a GET request doesn't have the Content-Length or Transfer-encoding: chunked field, what happens? How does the client know when the message ends?
回答1:
RFC 7230 section 3.3.3 contains a nice checklist of conditions for finding the message body size. Essentially it says the answer depends on what the status code is. The relevant conditions being #1 and #7.
"1. Any response ... with a 1xx (Informational), 204 (No Content), or 304 (Not Modified) status code is always terminated by the first empty line after the header fields, regardless of the header fields present in the message, and thus cannot contain a message body."
"7. Otherwise, this is a response message without a declared message body length, so the message body length is determined by the number of octets received prior to the server closing the connection."
Its also worth knowing that the message may continue after the end of the body portion. RFC 7230 section 4.4 defines a Trailers feature where the payload may be followed by a second set of mime headers. If those exist the message ends where they do.
回答2:
According to the specification
The length of a message body is determined by one of the following (in order of precedence):
- [...]
- Otherwise, this is a response message without a declared message body length, so the message body length is determined by the number of octets received prior to the server closing the connection.
The client needs to detect that the connection is closed.
来源：https://stackoverflow.com/questions/30339894/what-happens-in-http-response-to-a-get-request-without-content-length-or-transfe