IWSDOutboundAttachment::Write method (wsdattachment.h)

Sends attachment data to the remote host using a MIME container.


  [in]  const BYTE *pBuffer,
  [in]  DWORD      dwBytesToWrite,
  [out] LPDWORD    pdwNumberOfBytesWritten


[in] pBuffer

Pointer to a buffer containing the output data. The application program is responsible for allocating and freeing this data buffer.

[in] dwBytesToWrite

Number of bytes to send to the remote host from pBuffer.

[out] pdwNumberOfBytesWritten

Pointer to a DWORD containing the number of bytes of data actually sent to the remote host.

Return value

Possible return values include, but are not limited to, the following:

Return code Description
Method completed successfully.
pdwNumberofBytesWritten is NULL.
pBuffer is NULL.
The outbound attachment interface has not been initialized. Call WSDCreateOutboundAttachment to initialize the interface.
Internal buffers were not available. The data was not accepted and queued for transmission.


The Write method allows an application program to send arbitrary data to a remote host as a MIME-encapsulated message attachment. The first call to Write opens the outbound attachment stream and initiates transmission of the HTTP headers, envelope data, and the MIME-encoded application data. Subsequent calls to Write will send additional blocks of MIME-encoded application data until the application makes a call to Close, which closes the attachment stream and finishes the transmission of the message envelope data and headers.

The Write operation may block under several conditions. On the initial operation, Write will block until the HTTP headers and XML content have been transmitted. When sending multiple attachments in a single message, the first call to Write on any attachment may block until any prior attachment streams have been completely transmitted. Write may block for up to 30 seconds (per HTTP transmission timeouts) if the remote host does not reply.

If an error occurs in establishing a connection or transmitting headers, Write will return the error code immediately. If a data transfer error occurs, the error may be delayed to a future call of Write or Close.

The Write method may return successfully after a failed Write attempt that returned STG_S_BLOCK. A subsequent success indicates that the internal buffers were freed for use after the initial failed attempt. When STG_S_BLOCK is received by an application, the application can either resend the same data using the Write method or terminate the data transfer using the Abort method.


Minimum supported client Windows Vista [desktop apps only]
Minimum supported server Windows Server 2008 [desktop apps only]
Target Platform Windows
Header wsdattachment.h (include Wsdapi.h)
DLL Wsdapi.dll

See also