A client application posts a WM_DDE_REQUEST or WM_DDE_POKE message to perform a one-time data transfer with a server application. The item-name portion of the shared-memory object passed with the message contains the name of the desired item. When the client posts a WM_DDE_POKE message, the data portion of the shared-memory object contains the data being sent to the server.

If the server can satisfy the request, it renders the item in the requested format and includes it, with a DDESTRUCT data structure, in a shared-memory object and posts a WM_DDE_DATA message to the client, as shown in the following code fragment:

/* The DDE data structure is passed, and    */
/* the client should have shared it with us */
pDDEdata  = (PDDESTRUCT)mp2;
szReqItem = (BYTE *)(pDDEdata+(pDDEdata->offszItemName));
ShowMessage(szReqItem);

/*  We support item status, but not anything else */
if (!strcmpi(szReqItem, szItem))
   {
      ShowMessage("sending...");

       /* Get some sharable memory */
       DosAllocSharedMem((PVOID)&mem,
                         NULL,
                         sizeof(DDESTRUCT)+21,
                         PAG_COMMIT |
                         PAG_READ |
                         PAG_WRITE |
                         OBJ_GIVEABLE);

       /*  Get the server's id and give it access to the */
       /*  shared memory                                 */
       WinQueryWindowProcess(hClientWnd, &pid, &tid);
       DosGiveSharedMem(&mem, pid, PAG_READ | PAG_WRITE);

       /*  Setup DDE data structures                                 */
       /*  (11 byte name length, 10 plus NULL, 10 byte data length)  */
       pDDEdata           = (PDDESTRUCT)mem;
       pDDEdata->cbData   = 10;             /* Data length           */
       pDDEdata->fsStatus = 0;              /* Status                */
       pDDEdata->usFormat = DDEFMT_TEXT;    /* Text format           */

       /*  Go past end of structure for the name */
       pDDEdata->offszItemName = sizeof(DDESTRUCT);

       /*  Go past end of structure (and name) for the data  */
       pDDEdata->offabData = sizeof(DDESTRUCT)+11;
       strcpy((BYTE *)(pDDEdata+(pDDEdata->offabData)), szStatus);
       WinDdePostMsg(hClientWnd,
                     hwnd,
                     WM_DDE_DATA,
                     pDDEdata,
                     DDEPM_RETRY);
   }

   else
   {
       ShowMessage("rejecting...");
       pDDEdata->cbData   = 0;                  /* Data length */
       pDDEdata->fsStatus = DDE_NOTPROCESSED;   /* Status      */
       pDDEdata->usFormat = DDEFMT_TEXT;        /* Text format */
       WinDdePostMsg(hClientWnd,
                     hwnd,
                     WM_DDE_ACK,
                     pDDEdata,
                     DDEPM_RETRY);
   }
   ShowMessage("sent...");