This is a based on such a surface level understanding of one type of posix socket. Calling close twice on a socket is a normal allowed thing, particularly for non blocking sockets. Datagram sockets can be operated with bind, without bind, with connect and bind and with both called multiple times.

Some of what you said is true, but you definitely can’t call close multiple times on the same file descriptor. close always immediately drops the file descriptor and isn’t like non-blocking socket operations that you have to try repeatedly until they succeed. You could, however, create multiple file descriptors pointing to the same socket with dup or other methods, in which case you’d need to close all of them to disconnect the socket.