errno 76 (EPROCUNAVAIL): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: the selected remote program and version do not implement the requested procedure number.

Could be also:
Constant	Type	OS
ENOTUNIQ	errno	Linux
FATAL_UNHANDLED_HARD_ERROR	BugCheck Code	Windows

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ENOTUNIQ	EBADFD

EPROCUNAVAIL

EPROCUNAVAIL is Darwin’s ONC RPC error for a procedure that the selected remote program cannot provide. The RPC program and its version may be valid, and the RPC message may be accepted, but the proc number named by the call is not supported by that program version.

RFC 5531 distinguishes PROC_UNAVAIL from both PROG_UNAVAIL and PROG_MISMATCH. That distinction matters during diagnosis: if the program is absent, inspect registration and routing; if its version is incompatible, inspect the returned version range; if only the procedure is unavailable, inspect the client’s procedure number and interface contract for the version that was actually selected.

Diagnostic sequence

Record the RPC program number, program version, procedure number, transport, endpoint, and xid. The procedure number is essential evidence for this code.
Compare the client’s generated RPC stubs or interface definitions with the server implementation deployed at the target endpoint.
Check whether the service intentionally omits the procedure in the selected version, or whether a compatibility proxy routes the request to an implementation with a reduced API surface.
Do not treat it as a malformed argument error. GARBAGE_ARGS means a procedure cannot decode parameters, whereas PROC_UNAVAIL says the procedure itself is unsupported.

Commonly confused RPC outcomes

EPROGUNAVAIL: the requested program is not exported.
EPROGMISMATCH: the program is available but its requested version is unsupported.
EPROCUNAVAIL: the program/version is selected, but the requested procedure is not implemented.

References

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