Callback Function

To receive status notices, the application must implement a TAPI lineCallbackFunc function to establish a way to communicate with TAPI. The callback function is used for notifying applications of changes in the status of calls, lines, and phone devices. TAPI uses the callback function to send messages to an application.

For example, the LINE_REPLY message, sent to the Windows CE–based application, carries the request identifier and an error indicator. Only the application that issued the request receives the reply message, but when the request causes changes in the device state or call, other related applications might also receive event-related messages through the callback function.