os.close(fd) of a socket fd does not work some platforms, e.g. Windows. In the past we have used socket.socket(fileno=fd).close() to close a socket in a platform independent way. With #28134 it may no longer work in all cases, most noticeable when the socket has neither been connected nor bound yet and auto-detection of type and family is used.

Instead of adding more hacks, I propose to add a socket.close(fd) function as cross-platform way to close a socket fd. It won't be the first function that mimics an o' module function. The socket module already has the undocumented socket.dup(fd) function.

New changeset d0e31b980f18101738d0ec518cb991a5fb73fe93 by Christian Heimes in branch 'master':
bpo-32454: socket closefd (#5048)
https://github.com/python/cpython/commit/d0e31b980f18101738d0ec518cb991a5fb73fe93