TcQueryInterface function (traffic.h)

Article
02/22/2024

The TcQueryInterface function queries traffic control for related per-interface parameters. A traffic control parameter is queried by providing its globally unique identifier (GUID). Setting the NotifyChange parameter to TRUE enables event notification on the specified GUID, after which notification events are sent to a client whenever the queried parameter changes. GUIDs for which clients can request notification are found in the GUID entry; the column titled "Notification" denotes which GUIDs are available for notification.

Syntax

ULONG TcQueryInterface(
  [in]      HANDLE  IfcHandle,
  [in]      LPGUID  pGuidParam,
  [in]      BOOLEAN NotifyChange,
  [in, out] PULONG  pBufferSize,
  [out]     PVOID   Buffer
);

Parameters

[in] IfcHandle

Handle associated with the interface to be queried. This handle is obtained by a previous call to the TcOpenInterface function.

[in] pGuidParam

Pointer to the globally unique identifier (GUID) that corresponds to the traffic control parameter being queried.

[in] NotifyChange

Used to request notifications from traffic control for the parameter being queried. If TRUE, traffic control will notify the client, through the ClNotifyHandler function, upon changes to the parameter corresponding to the GUID provided in pGuidParam. Notifications are off by default.

[in, out] pBufferSize

Indicates the size of the buffer, in bytes. For input, this value is the size of the buffer allocated by the caller. For output, this value is the actual size of the buffer, in bytes, used by traffic control.

[out] Buffer

Pointer to a client-allocated buffer into which returned data will be written.

Return value

Note that, with regard to a requested notification state, only a return value of NO_ERROR will result in the application of the requested notification state. If a return value other than NO_ERROR is returned from a call to the TcQueryInterface function, the requested change in notification state will not be accepted.

Return code	Description
NO_ERROR	The function executed without errors.
ERROR_INVALID_HANDLE	Invalid interface handle.
ERROR_INVALID_PARAMETER	Invalid or NULL parameter.
ERROR_INSUFFICIENT_BUFFER	The buffer is too small to store the results.
ERROR_NOT_SUPPORTED	Querying for the GUID provided is not supported on the provided interface.
ERROR_WMI_GUID_NOT_FOUND	The device did not register for this GUID.
ERROR_WMI_INSTANCE_NOT_FOUND	The instance name was not found, likely because the interface is in the process of being closed.

Remarks

Note Use of the TcQueryInterface function requires administrative privilege.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	traffic.h
Library	Traffic.lib
DLL	Traffic.dll