3.2.4 Message Processing Events and Sequencing Rules
As defined in section 3.1.4.1, requests sent with the LnkSvrMessage method are sent via the pMsg parameter, which is a TRKSVR_MESSAGE_UNION structure. In that structure is a MessageType field, defined by the TRKSVR_MESSAGE_TYPE enumeration, which indicates the format of the message data in the MessageUnion field.
Generally, requests are sent via fields on the TRKSVR_MESSAGE_UNION structure, and responses from the server are returned to the client by updating fields in this same structure. The client completion handling is covered in subsequent subsections for each type of message, according to the MessageType field of the TRKSVR_MESSAGE_UNION structure.
Except where otherwise stated, the client MUST ignore all fields in the TRKSVR_MESSAGE_UNION structure on completion of the LnkSvrMessage request.