TCP Puzzlers
Idle but half-dead TCP connections will eventually time out.  It can take hours, though, on some systems.[1] Early thinking was that if you have a Telnet session open, TCP itself should not time out.  The Telnet server might have a timeout, but it wasn't TCP's job to decide how long you get for lunch.<p>Today most servers have shorter timeouts, mostly as a defense against denial of service attacks. But it's often the HTTP server, not the TCP level, that times out first.<p>[1] <a href="https://blogs.technet.microsoft.com/nettracer/2010/06/03/things-that-you-may-want-to-know-about-tcp-keepalives/" rel="nofollow">https://blogs.technet.microsoft.com/nettracer/2010/06/03/thi...</a>