What does NTSTATUS 0xC00000B1 (STATUS_PIPE_CLOSING) mean?

STATUS_PIPE_CLOSING

The pipe handle is already in closing state

Find the close or disconnect that began before the current I/O. New work should stop once the instance enters closing state, while outstanding operations complete or are cancelled according to the API contract.

This status means the instance has started teardown. Later reads, writes, connects, or mode changes should not be treated as new protocol failures because the handle lifetime is ending.

What to inspect

• Check for concurrent CloseHandle, DisconnectNamedPipe, or cancellation.
• Stop scheduling new I/O after closing begins.
• Treat repeated failures as cleanup fallout if teardown is already in progress.

References for STATUS_PIPE_CLOSING

• Microsoft Open Specifications: NTSTATUS values
• Microsoft: Named Pipes
• Microsoft: Named Pipe Type, Read, and Wait Modes
• Microsoft: Named Pipe Operations