PC/3270 Response

PC/3270 receives the Start Read SF and returns an ACK message if it can start the Read SF. Otherwise a negative ACK message is returned to the client with one of the following return codes in the low-order byte of the wStatus field:

WM_DDE_ACK(wStatus, aSF)


Return Code	Explanation
1	Read SF is already started.
3	No prior Set Structured Field Service Condition function was called.
6	The specified format is not valid.
9	A system error occurred.

Once the Read SF has started, the client receives DATA messages of the structured field:

WM_DDE_DATA(hData, aSF)

where:

hData	Identifies a handle to a Windows global memory object containing: `typedef struct tagSFDATA { unsigned unused:12, // unsigned fRelease:1, // unsigned fReserved:3; // int cfFormat; // Always CF_DSPTEXT WORD uSFLength; // Length of SF data char szSFData[1]; // SF data } SFDATA, FAR *lpSFDATA;`

hData

Identifies a handle to a Windows global memory object containing:

typedef struct tagSFDATA
{
 unsigned   unused:12,             //
 unsigned   fRelease:1,            //
 unsigned   fReserved:3;           //
 int        cfFormat;              // Always CF_DSPTEXT
 WORD       uSFLength;             // Length of SF data
 char       szSFData[1];           // SF data
} SFDATA, FAR *lpSFDATA;

The DATA messages continue until a Stop Read SF message is sent to PC/3270.