问题
I understand that in HTTP 1.0, the content of a response is terminated by closing the connection.
In HTTP 1.1, keep-alive connections were introduced, enabling multiple requests and responses in a single TCP connection.
When multiple messages are sent over the same connection, there needs to be a mechanism that defines where one message ends and the next message starts.
By testing, I found out that this works when I set the content-length header in a response. By knowing the content length, the client knows when the content is fully received and can parse the next response.
My question is:
Is it possible to send multiple responses in a keep-alive connection without setting the content-length header?
If yes, how?
For clarification: I am thinking about scenarios where the length of the response is not known when starting to send it to the client and I would like to know if closing the connection is the only way to implement that.
回答1:
The Transfer-Encoding header is what I was looking for.
By setting the transfer-encoding to chunked, it is possible to omit the Content-Length header.
In the chunked transfer encoding, a message can be sent in multiple chunks for which the length is known. To terminate a message, a chunk with length zero is sent.
This makes it possible to have a keep-alive connection and still send messages where the length is unknown when starting to send them.
来源：https://stackoverflow.com/questions/49256096/are-http-keep-alive-connections-possible-without-content-length-headers