What does errno 135 (EPROTONOSUPPORT) mean?

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: A UCRT POSIX-supplement status for a protocol unsupported by the requested socket configuration.

Could be also:
Constant	Type	OS
ERROR_IS_SUBSTED	Win32 error	Windows

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EPROTO	EPROTOTYPE

EPROTONOSUPPORT

EPROTONOSUPPORT concerns the protocol requested when a socket is created or configured. It differs from EAFNOSUPPORT, which concerns the address family, and from EPROTOTYPE, which concerns a protocol used with the wrong socket type. The three values identify different parts of the socket contract.

Winsock provides the native WSAEPROTONOSUPPORT status through WSAGetLastError(). Preserve the requested family, type, and protocol number or name; without all three, a log cannot tell whether the provider is absent or the combination is invalid.

Verify the protocol selection

Record arguments to socket exactly: family, type, protocol, and any provider-selection mechanism.
Check whether the application is requesting a protocol that is unavailable on the target Windows configuration or disabled by policy.
Do not substitute a different protocol automatically if that changes reliability, ordering, security, or framing semantics.
For portable code, keep explicit capability detection instead of relying on numeric protocol values from another platform.

References

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