This is strictly a violation of the TCP specification

What this post added

This post details the debugging of a rare 522 error, tracing it back to a subtle issue where an application leaking sockets in the CLOSE_WAIT state on the loopback interface caused connection timeouts for new connections. It highlights how this application-level problem, not a network issue, can lead to symptoms that appear to violate TCP specifications, impacting Cloudflare's edge connectivity.