How server knows to close the connection of websocket when website tab is closed

Question

I created a websocket (with perl Net::WebSocket::Server but I think it does not matter). My question is that when I close the website tab(not necessarily the whole browser) the server will disconnect the specific socket (my disconnect event is called). How the server manage to know that? I can not find a straight detailed description.

Answer 1

If the browser closes one end of a socket (either explicitly via close, or implicitly because the process exits) the server at the other end of the socket connection will be notified that the socket is now closed. That's just part of how TCP works. Even if the message got lost and the server thought the socket was still open, when it tried to send data it would eventually work out that the other end was not acknowledging the packets and would drop the connection.

In the case of a browser tab, it's reasonable to assume that the browser will cleanup/close any resources associated with a tab that is being closed.