Windows error 10091 (WSASYSNOTREADY): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: WSASYSNOTREADY wSAStartup cannot function at this time because the underlying system it uses to provide network services is currently unavailable.

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WSAEREMOTE	WSAVERNOTSUPPORTED

WSASYSNOTREADY

WSASYSNOTREADY means that the underlying network subsystem is not ready for use. It is normally returned while initializing Winsock rather than by an individual socket operation.

Where to look

The failure can be caused by a local networking stack or service problem, not by a remote host. Retrying the same socket call without restoring local networking availability is unlikely to help.

What to check

Adapter state, network-related services, and recent driver or VPN changes.
System event logs for startup or protocol-stack failures.
That the application performs WSAStartup during initialization and handles a failure before creating sockets.

Microsoft: WSAStartup · Microsoft: Windows Sockets Error Codes

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