Knowledge

WSA_QOS_EFILTERCOUNT - 11021 (0x2B0D)

An incorrect number of QOS FILTERSPECs were specified in the FLOWDESCRIPTOR.

Updated: Feb 21, 2026

Technical Background

The WSA_QOS_EFILTERCOUNT error, with the numeric code 11021 (0x2B0D), is a specific error related to Windows Socket Quality of Service (QoS) operations. This error indicates that an incorrect number of QoS FILTERSPECs were specified in the FLOWDESCRIPTOR.

Error Details

The WSA_QOS_EFILTERCOUNT error occurs when the number of QoS FILTERSPECs provided does not match the expected or required number for a given operation. The FLOWDESCRIPTOR is a structure used to define Quality of Service requirements for network flows, and it contains multiple FILTERSPEC structures that specify the QoS parameters.

Common Causes

  • Invalid Parameter Values: The number of FILTERSPECs specified in the FLOWDESCRIPTOR does not match the expected value. This can occur if the application incorrectly sets the count or if there is a mismatch between the application's expectations and the system requirements.
  • Incorrect Object Type: Although this error specifically relates to QoS operations, it is important to ensure that the object types being manipulated are correctly identified and handled by the application.

Real-World Context

This error typically arises in scenarios where applications need to configure network flows with specific Quality of Service requirements. For example, when setting up a socket for real-time data transmission, the application must specify the appropriate number of QoS FILTERSPECs to ensure proper flow control and prioritization.

Is This Error Critical?

The criticality of this error depends on the context in which it occurs. If the operation is part of a critical network service, such as a real-time communication protocol, then this error could lead to significant issues. However, for non-critical operations, the impact may be minimal.

How to Diagnose

To diagnose this issue, developers should review the following:

  • Review Operation Context: Ensure that the operation context is correct and that the application is using the appropriate FLOWDESCRIPTOR structure.
  • Validate Parameters: Verify that the number of FILTERSPECs specified in the FLOWDESCRIPTOR matches the expected value. This can be done by checking the documentation or source code for the specific API call being used.
  • Confirm Object Types: Confirm that the object types are correctly identified and handled within the application. Ensure that the application is not attempting to use unsupported operations or incorrect data types.

How to Resolve

To resolve this issue, developers should take the following steps:

  • Correct Parameter Usage: Ensure that the number of FILTERSPECs specified in the FLOWDESCRIPTOR matches the expected value for the operation. This may involve adjusting the application code to correctly set the count or by ensuring that the correct number of FILTERSPEC structures are provided.
  • Adjust Operation Context: If the operation context is incorrect, adjust it to ensure that the application is using the appropriate parameters and data types.

Developer Notes

Developers should be aware that this error can occur due to a mismatch between expected and actual parameter values. It is important to thoroughly test applications that use QoS operations to ensure that all parameters are correctly set and that the operation context is valid.

Related Errors

  • WSA_QOS_EFLOWDESC: Indicates an issue with the FLOWDESCRIPTOR structure itself, such as invalid or missing fields.
  • WSA_QOS_EFLOWSPEC: Relates to issues with individual FILTERSPEC structures within the FLOWDESCRIPTOR.

FAQ

Q: What does WSA_QOS_EFILTERCOUNT mean?

A: The WSA_QOS_EFILTERCOUNT error indicates that an incorrect number of QoS FILTERSPECs were specified in the FLOWDESCRIPTOR. This can occur if the application incorrectly sets the count or if there is a mismatch between the application's expectations and the system requirements.

Q: How can I prevent this error?

A: To prevent this error, ensure that the number of FILTERSPECs specified in the FLOWDESCRIPTOR matches the expected value. Verify that the operation context is correct and that all parameters are set correctly according to the API documentation.

Summary

The WSA_QOS_EFILTERCOUNT error occurs when an incorrect number of QoS FILTERSPECs are specified in a FLOWDESCRIPTOR. This can be caused by invalid parameter values or incorrect object types. Developers should review and validate their parameters, ensuring that they match the expected values for the operation context.