What does NTSTATUS 0xC00000AC (STATUS_PIPE_NOT_AVAILABLE) mean?

STATUS_PIPE_NOT_AVAILABLE

The named pipe exists, but no instance is ready to connect

Confirm that the named-pipe server created an instance for the requested name and scope. Distinguish no available server instance from an access denial or a client using the wrong namespace.

This status usually means the pipe namespace entry or server process exists, but every instance is connected, closing, or otherwise not in a listening state. It is a pipe-instance state problem rather than a path parsing problem.

What to inspect

• Inspect how many instances the server created.
• Check for clients holding pipe handles longer than expected.
• Differentiate this from STATUS_OBJECT_NAME_NOT_FOUND, where the pipe name itself is absent.

References for STATUS_PIPE_NOT_AVAILABLE

• Microsoft Open Specifications: NTSTATUS values
• Microsoft: Named Pipes
• Microsoft: CreateNamedPipe