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Using this support function, your ISAPI extension can request that IIS attempt to read from the client asynchronously. In order for this function to work properly, however, you must have specified a special callback function, which IIS will call when the asynchronous read has completed. This callback function can be set using the ServerSupportFunction request HSE_REQ_IO_COMPLETION.

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


  • ConnID
    Specifies the connection identifier of the client to which the response data should be sent.

  • dwServerSupportFunction
    The name of the Server Support function, which in this case must be set to HSE_REQ_ASYNC_READ_CLIENT.

  • lpvBuffer
    Points to the buffer into which IIS should write the data read from the client.

  • lpdwSizeofBuffer
    Points to the size of the buffer indicated by lpvBuffer.

  • lpdwDataType
    Must be set to HSE_IO_ASYNC.


If your extension has not set a callback function before calling the ServerSupportFunction HSE_REQ_ASYNC_READ_CLIENT request, then your extension will receive an error from IIS.


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.

See Also