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when a user use browser to visit a website, it is the browser who initiates a TCP tear-down , namely it is the browser who sends the FIN/ACK first.

is it possible that web server sends the FIN/ACK first?

if so, in what cases will the web server sends the FIN/ACK first?


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up vote 2 down vote accepted

Sure! In HTTP, either side can initiate the teardown. The most obvious scenario that comes to mind is that an HTTP connection has been kept open for HTTP keepalive, but after a while the server decides it has too many open sockets and terminates some of them. Another case would be if the client is in the middle of sending a request with a body (such as PUT or POST) and the server discovers an error, replies with an error, and tears down its side of the connection without waiting for the client to finish transmitting the body.

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