At any time, either the client or the server may terminate a DDE conversation by posting a WM_DDE_TERMINATE message, as shown in the following code fragment:

WinDdePostMsg(hwndDest,                /* Handle of destination    */
              hwndSource,              /* Handle of source         */
              WM_DDE_TERMINATE,        /* Message                  */
              NULL,                    /* No shared-memory pointer */
              DDEPM_RETRY);            /* Retry                    */