Not sure, but maybe this is somehow related to getsockname() blocks indefinitely?.

Also, I had myself once experienced similar weirdness with getsockname depending on the setting of SO_EXCLUSIVEADDRUSE (Windows-specific socket option), though you'd think that both should be unrelated.  (Unfortunately, I can no longer remember the details, nor can I come up with a test case that would reproduce the issue — but maybe it rings a bell with someone else...)