macOS kernel return 7 (KERN_NOT_RECEIVER): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: The task does not hold the receive right required for the specified Mach port.

Could be also:
Constant	Type	OS
ERROR_ARENA_TRASHED	Win32 error	Windows
ippStsLnZeroArg	Intel Ipp Status	Any
E2BIG	errno	Any
INVALID_SOFTWARE_INTERRUPT	BugCheck Code	Windows

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KERN_RESOURCE_SHORTAGE	KERN_NO_ACCESS

KERN_NOT_RECEIVER

KERN_NOT_RECEIVER is a Mach port-rights error. The task named in the operation does not own the receive right for the port argument. A Mach port is not just a globally usable number: rights are capabilities held in a task's own port namespace.

Mach's communication model normally has one receiver for a port and potentially many senders. A send right permits sending messages, but it does not authorize receiving from the port's queue or managing the receive-side state. That is why having a valid-looking port name or a send right is not enough for operations that require the receiver.

What to verify

Which task owns the receive right and which task's port namespace the call addresses.
Whether a right was transferred as a send right, send-once right, or receive right.
Whether a port was destroyed, moved, or replaced during setup or teardown.
Whether the API is trying to manage a port set or receive queue when the caller only has a sending capability.

Diagnosing this as an ordinary permission error can be misleading. The central question is capability ownership: Mach operations are permitted according to the specific kind of right held by the relevant task.

References

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