Start method

Starts the operation.


HRESULT retVal = object.Start(szUrl, pOIProtSink, pOIBindInfo, grfPI, dwReserved);


  • szUrl [in]
    Type: LPCWSTR

    The address of a string value that contains the URL. For a pluggable MIME filter, this parameter contains the MIME type.

  • pOIProtSink [in]
    Type: IInternetProtocolSink

    The address of the protocol sink provided by the client.

  • pOIBindInfo [in]
    Type: IInternetBindInfo

    The address of the IInternetBindInfo interface that the protocol gets download-specific information from.

  • grfPI [in]
    Type: DWORD

    An unsigned long integer value that contains the flags to determine whether the method parses or parses and downloads the URL. This can be one of the PI_FLAGS values.

  • dwReserved [in]
    Type: HANDLE_PTR

    For pluggable MIME filters, contains the address of a PROTOCOLFILTERDATA structure. Otherwise, it is reserved and must be set to NULL.


INET_E_USE_DEFAULT_PROTOCOLHANDLER can only be returned by a pluggable namespace handler or MIME filter. Only a single, permanently registered asynchronous pluggable protocol handler can be assigned to a particular scheme, such as FTP, so there are no other handlers to default to.

To use INET_E_USE_DEFAULT_PROTOCOLHANDLER, the pluggable protocol handler object must support aggregation. For more information, see COM Aggregation.