errno 96 (EPFNOSUPPORT): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: the requested protocol family is not supported by this Linux endpoint.

Could be also:
Constant	Type	OS
ENODATA	errno	Mac
EDESTADDRREQ	errno	Solaris
PROCESS_INITIALIZATION_FAILED	BugCheck Code	Windows

Previous	Next
ENOTSOCK	ENODATA

EPFNOSUPPORT

EPFNOSUPPORT belongs to the socket protocol-family selection boundary. It is close to EAFNOSUPPORT, but the useful distinction is that protocol family, address family, socket type, and protocol number are separate parts of the socket contract.

When this appears, log the exact family, socket type, protocol, namespace, and kernel configuration. The fix is not to reconnect or wait; the requested family is not available in that environment, or the application selected an incompatible family/type/protocol combination.

Compare nearby socket errors

EAFNOSUPPORT: address family unsupported for the protocol.
EPROTONOSUPPORT: protocol unsupported.
ESOCKTNOSUPPORT: socket type unsupported.
EPFNOSUPPORT: protocol family itself is unsupported.

Linux socket(2) · Linux errno(3) · Linux UAPI errno definitions

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