What does Windows error code 10066 (WSAENOTEMPTY) mean?

WSAENOTEMPTY

WSAENOTEMPTY is unusual in a Winsock error list because its semantics are filesystem-oriented. Microsoft retains BSD-compatible error constants in the Windows Sockets namespace, and also warns that some values defined in Winsock2.h are not returned by any Winsock function.

What this means in network software

If a networking process logs WSAENOTEMPTY, do not diagnose packet loss or a remote socket state from the name. First identify the failing function. A portable runtime, local cache cleanup, network-filesystem helper, or error-mapping wrapper may be reporting a directory operation through a common WSA* code path.

Useful checks

• Capture the API and source module that set the error.
• Check whether a temporary or cache directory is being removed while files remain open or present.
• Verify that the code did not blindly prefix a POSIX errno name with WSA.

For a real socket argument problem, Winsock normally reports socket-specific codes such as WSAENOTSOCK, WSAENOTCONN, or WSAESHUTDOWN.

Microsoft: Winsock error codes · Microsoft: BSD error compatibility · POSIX: errno.h

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