LINE_REPLY

This message is sent to report the results of function calls that completed asynchronously.

At a Glance

Syntax

LINE_REPLY dwDevice = (DWORD) 0;
dwCallbackInstance = (DWORD) hCallback;
dwParam1 = (DWORD) idRequest; dwParam2 = (DWORD) Status;
dwParam3 = (DWORD) 0;

Parameters

dwDevice

Not used.

dwCallbackInstance

Returns the application’s callback instance.

dwParam1

Specifies the request identifier for which this is the reply.

dwParam2

Specifies the success or error indication. The application should cast this parameter into a LONG. Zero indicates success; a negative number indicates an error.

dwParam3

Unused.

Return Values

None.

Remarks

Functions that operate asynchronously return a positive request identifier value to the application. This request identifier is returned with the reply message to identify the request that was completed. The other parameter for the LINE_REPLY message carries the success or failure indication. Possible errors are the same as those defined by the corresponding function. This message cannot be disabled.

In some cases, an application may fail to receive the LINE_REPLY message corresponding to a call to an asynchronous function. This occurs if the corresponding call handle is deallocated before the message has been received.

Note   When an application invokes any asynchronous operation that writes data back into application memory, the application must keep that memory available for writing until a LINE_REPLY or LINE_GATHERDIGITS message is received.