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3.2.4.1 LnkSvrMessageCallback (Opnum 1)

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The LnkSvrMessageCallback method is an RPC callback method that provides a means for the DLT Central Manager server to call back to the client during a LnkSvrMessage call. As defined in section 3.1.4, this callback only occurs for SYNC_VOLUMES messages (for an example of this message, see section 3.2.5.3).

For more details on when this callback is used by the server, see section 3.1.4.4.

 [callback] HRESULT LnkSvrMessageCallback(
   [in, out] TRKSVR_MESSAGE_UNION* pMsg
 );

pMsg: Pointer to a message, in the format of a TRKSVR_MESSAGE_UNION structure. The MessageType field in this structure MUST be set to SYNC_VOLUMES.

Return Values: The return value is typed as an HRESULT, but for this method, a value of zero indicates success, and all other values indicate failure. Any nonzero value MUST be treated identically as a failure value.

The client MUST respond to this request by executing the steps in section 3.2.4.4 on each of the TRKSVR_SYNC_VOLUME structures in the TRKSVR_CALL_SYNC_VOLUMES structure within the pMsg parameter. In this way, the client is responding as though it received the updated structure in the completion of the LnkSvrMessage request.

If any subrequest indicates a failure—that is, if the hr field of any TRKSVR_SYNC_VOLUME structure is not zero—the client MUST return to the server with a return value that indicates failure.

For example, in a typical case where this callback method is used, processing proceeds in the following order:

  • The client sends a SYNC_VOLUMES message to the server by calling LnkSvrMessage, as described, for example, in section 3.2.5.3.

  • The server processes the request, updates the TRKSVR_CALL_SYNC_VOLUMES array in the request, and calls LnkSvrMessageCallback on the client.

  • The client processes the subrequests in the updated TRKSVR_CALL_SYNC_VOLUMES array, as defined in section 3.2.4.4.

  • The client returns from the LnkSvrMessageCallback method to the server.

  • The server sets the cProcessed field of the TRKSVR_CALL_SYNC_VOLUMES structure to zero, and returns from the LnkSvrMessage method to the client.

  • The client again performs the processing defined in section 3.2.4.4. But because the cProcessed field has been set to zero, the client takes no additional action, as defined in that section.