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ServerSupportFunction Extension Function

The ServerSupportFunction function is a callback function that is supplied in the EXTENSION_CONTROL_BLOCK Structure that is associated with the current HTTP request. ServerSupportFunction can be used to perform a variety of tasks.


If a parameter is designated as unused in a particular support function, you should set that parameter to NULL.

BOOL WINAPI ServerSupportFunction(
      HCONN ConnID,
      DWORD dwServerSupportFunction,
      LPVOID lpvBuffer,
      LPDWORD lpdwSizeofBuffer,
      LPDWORD lpdwDataType


Return Values

If the function succeeds, the return value is TRUE. If the function fails, the return value is FALSE. The Win32? GetLastError function can be used to determine why the call failed. The following are the possible error values.

Return code



Bad connection handle, or invalid values, in either lpszVariableName or lpdwSizeOfBuffer.


Bad or unsupported variable identifier.


Buffer too small. The required buffer size is *lpdwSizeofBuffer.


The data requested is not available.


Client: Requires Windows XP Professional, Windows 2000 Professional, or Windows NT Workstation 4.0.

Server: Requires Windows Server 2003, Windows 2000 Server, or Windows NT Server 4.0.

Product: IIS

Header: Declared in httpext.h.