title: Why is port not immediately released after the socket closes?
body: <p>I found that by default OS does not immediately release the port that my server socket uses after the server shuts down. By giving <code>SO_REUSEADDR</code> when setting up the socket can avoid this problem, but I don't understand why it's useful to hold the port for a while. If the server shuts down, the socket closes, any data transmitted to this port wouldn't be processed anyways right?</p>