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STATUS_INSTANCE_NOT_AVAILABLE
All pipe instances are busy or unavailable
These statuses belong to the Windows named-pipe path. For STATUS_INSTANCE_NOT_AVAILABLE, A named pipe can have multiple instances with the same name, but each instance has its own state, buffer, handles, type mode, read mode, and wait mode.
A client reached the pipe name, but the server has no instance that can accept the connection at that moment. This is different from a missing pipe name: the server side may exist, but the instance pool is exhausted or not listening.
For STATUS_INSTANCE_NOT_AVAILABLE, for diagnostics, record the pipe name, server/client end, instance count, blocking versus nonblocking mode, byte versus message mode, overlapped operation state, and whether the handle is connected, listening, closing, or disconnected.
What to inspect
- Check the maximum instance count passed to CreateNamedPipe.
- Verify that the server creates a replacement instance after each connection.
- Use WaitNamedPipe-style retry only when the server is expected to create another instance.
References for STATUS_INSTANCE_NOT_AVAILABLE
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