Knowledge

WSASYSNOTREADY - 10091 (0x276B)

WSAStartup cannot function at this time because the underlying system it uses to provide network services is currently unavailable.

Updated: Feb 21, 2026

Technical Background

The WSASYSNOTREADY error is a specific error code returned by the Windows Sockets (Winsock) API. This error indicates that the underlying system responsible for providing network services is currently unavailable, preventing the successful execution of certain operations.

Error Details

  • Error Name: WSASYSNOTREADY
  • Numeric Code: 10091 (0x276B)
  • Short Description: WSAStartup cannot function at this time because the underlying system it uses to provide network services is currently unavailable.

This error typically occurs when the Winsock subsystem, which manages network operations, is not properly initialized or is in a state where it cannot support network service requests. The WSAStartup function is used to initialize the Winsock library and prepare it for use, but if the underlying system is not available, this initialization fails.

Common Causes

  • Invalid Parameter Values: Incorrect parameters passed to WSAStartup, such as an invalid version number or a null pointer.
  • Incorrect Object Type: Attempting to perform operations that are not supported by the current state of the Winsock subsystem.
  • Exceeding Limits: The system may have reached its limit for network resources, preventing further initialization attempts.

Real-World Context

This error can occur in various scenarios where network services are required but the underlying infrastructure is unavailable. For example, it might happen if a network driver or service is not running, or if there is an issue with the system's networking configuration.

Is This Error Critical?

The criticality of this error depends on the application's requirements and the context in which it occurs. If the application relies heavily on network services, encountering WSASYSNOTREADY can lead to significant functionality issues. However, if the application is designed to handle such errors gracefully, the impact might be minimal.

How to Diagnose

To diagnose this error, follow these steps:

  1. Review Operation Context: Ensure that all necessary network services are running and configured correctly.
  2. Validate Parameters: Check the parameters passed to WSAStartup for correctness and completeness.
  3. Confirm Object Types: Verify that the application is attempting operations supported by the current state of the Winsock subsystem.
  4. Verify Input Data: Ensure that there are no corrupted or invalid data structures affecting network initialization.
  5. Check Limits or Constraints: Confirm that the system has not reached any resource limits that could prevent WSAStartup from succeeding.

How to Resolve

To resolve this error, consider these practical steps:

  • Correct Parameter Usage: Ensure all parameters passed to WSAStartup are valid and correctly configured.
  • Adjust Operation Context: If the underlying system is unavailable due to configuration issues, adjust the network settings or restart relevant services.
  • Restore Data: If data corruption is suspected, restore from a known good backup if available.
  • Retry Operation with Valid Inputs: Attempt to initialize Winsock again with valid inputs once the underlying issue has been resolved.

Developer Notes

Developers should be aware that WSASYSNOTREADY can occur in various scenarios and may require different troubleshooting approaches. It is essential to handle this error gracefully, providing appropriate feedback to users or logging relevant information for debugging purposes.

Related Errors

  • WSAEACCES (10013): Permission denied during network operation.
  • WSAENETDOWN (10050): Network is down; the specified network name is no longer available.
  • WSAENETUNREACH (10051): Network is unreachable; a required route is not present and no attempt to create one was made.

FAQ

Q: What does WSASYSNOTREADY mean?

A: WSASYSNOTREADY indicates that the underlying system for network services is unavailable, preventing successful initialization of Winsock.

Q: How can I prevent this error from occurring?

A: Ensure all necessary network services are running and configured correctly. Validate parameters passed to WSAStartup and verify the application's operation context.

Q: Can this error be ignored if my application does not rely on network services?

A: If your application does not depend on network services, you can safely ignore or handle this error as appropriate for your use case.

Summary

The WSASYSNOTREADY error is a specific indication that the Winsock subsystem cannot initialize due to an unavailable underlying system. This error requires careful handling and troubleshooting based on the application's context and the state of network services. By understanding its causes and implementing proper resolution strategies, developers can ensure robust network operations in their applications.