When TCP sockets refuse to die

In this blog post, the author discusses various scenarios where a TCP connection may notice issues with the other party going away. These scenarios include SYN-SENT, SYN-RECV, idle ESTABLISHED connections, busy ESTABLISHED connections, and zero-window ESTABLISHED connections. The author provides scripts to demonstrate the effects of timeout-related socket options under various network conditions. They also discuss how to tune a TCP connection to ensure that the remote host is actually up and provide tips for debugging networking issues.