errno 109 (EDESTADDRREQ): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: A UCRT POSIX-supplement status for a send operation that needs a destination address but was given none.

Could be also:
Constant	Type	OS
ERROR_BROKEN_PIPE	Win32 error	Windows
ETOOMANYREFS	errno	Linux
SESSION1_INITIALIZATION_FAILED	BugCheck Code	Windows

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ETOOMANYREFS	ETIMEDOUT

EDESTADDRREQ

EDESTADDRREQ indicates that a message-oriented operation needs a destination endpoint, but the caller has not provided one and the socket has no default peer. It is primarily a state-and-API contract issue, not a network reachability problem.

For Winsock, the native counterpart is WSAEDESTADDRREQ. A datagram socket can receive a destination from each sendto-style call or obtain a default peer through connect; those choices produce different application semantics, especially when the client communicates with multiple peers.

Make the addressing model explicit

For an unconnected datagram socket, pass a fully initialized destination address and its correct structure length on every send.
For a connected datagram socket, verify when the default peer was assigned and whether a reconnect or close reset that state.
Log the actual destination family, address, port, and scope information. A null or zeroed address is not equivalent to an automatic route choice.
Do not confuse this error with a remote refusal: the operation failed before a usable destination was selected.

References

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