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Introduce the way to connect DAServer by DDE interface with Microsoft DDEML(DDE Management Library).

Sample Screen

In this sample, it writes and the function of four is used, a connection to the DAServer, manual read operation, automatic read operation, manual poke operation.

Initial
Handler and DDE Conection that processes Callback from DAServer are defined.
HDDEDATA CALLBACK UdprocDdeCallback(UINT, UINT, HCONV, HSZ, HSZ, HDDEDATA, DWORD, DWORD); DWORD idInst=0; // hadle to DDE connection XACT *pxact=NULL; CONVCONTEXT CCFilter = { sizeof(CONVCONTEXT), 0, 0, 0, 0L, 0L, { sizeof(SECURITY_QUALITY_OF_SERVICE), SecurityImpersonation, SECURITY_STATIC_TRACKING, TRUE };

DDE Connection
The application name and the topic name of DDE are set, and the DDE connection is executed.
BOOL UdprocDdeConnect(CString cappname, CString ctopicname) { HSZ hszApp, hszTopic; HCONV hConv; int ret; if ((ret=DdeInitialize(&idInst, (PFNCALLBACK)UdprocDdeCallback, APPCMD_CLIENTONLY, 0L)) != DMLERR_NO_ERROR){ AfxMessageBox("Failed to DdeInitialize (%d)", ret); return true; } hszApp = DdeCreateStringHandle(idInst, cappname, 0); hszTopic = DdeCreateStringHandle(idInst, ctopicname, 0); if(!(hConv = DdeConnect(idInst, hszApp, hszTopic, &CCFilter))){ AfxMessageBox("Failed to DdeInitialize (%d)", ret); DdeFreeStringHandle(idInst, hszApp); DdeFreeStringHandle(idInst, hszTopic); return true; } DdeFreeStringHandle(idInst, hszApp); DdeFreeStringHandle(idInst, hszTopic); pxact = (XACT *)malloc(sizeof(XACT)); memset(pxact, 0, sizeof(pxact)); pxact->hConv = hConv; pxact->fsOptions = 0; pxact->ulTimeout = 1000; // TimeOut=1000ms return false; }

DDE Manual Read
In a synchronous reading by the DDE manual operation link, the return value of the DDEML function reaches the data value.
BOOL UdprocDdeRequest(CString citemname, CString& cdata) { DWORD dwLength; if(pxact == NULL) return false; pxact->hszItem = DdeCreateStringHandle(idInst, citemname, 0); pxact->wFmt = CF_TEXT; pxact->wType = XTYP_REQUEST; // DDE Reqeuest (dde manual link) pxact->hDdeData = DdeClientTransaction(NULL, 0, pxact->hConv, pxact->hszItem, pxact->wFmt, pxact->wType, pxact->ulTimeout, (LPDWORD)&pxact->Result); if (pxact->hDdeData) { cdata = DdeAccessData(pxact->hDdeData, &dwLength); } else { AfxMessageBox("Failed to DdeClientTransaction"); return true; } return false; }

DDE Poke
The value is written in the specified item name.
BOOL UdprocDdePoke(CString citemname, CString cval) { if(pxact == NULL) return false; pxact->hszItem = DdeCreateStringHandle(idInst, citemname, 0); // DDE Item pxact->wFmt = CF_TEXT; pxact->wType = XTYP_POKE; // DDE Poke pxact->hDdeData = DdeCreateDataHandle(idInst, (LPBYTE)(LPCTSTR)cval, cval.GetLength()+1, 0, NULL, pxact->wFmt, 0); DdeClientTransaction((LPBYTE)(LPCTSTR)cval, cval.GetLength()+1, pxact->hConv, pxact->hszItem, pxact->wFmt, pxact->wType, pxact->ulTimeout, NULL); return false; }

DDE automatic read
Callback Handler is called by registering the item name in asynchronous reading and DAServer by DDE automatic a link every time there is a change in the data value.
BOOL UdprocDdeAdvise(CString citemname) { if(pxact == NULL) return false; pxact->hszItem = DdeCreateStringHandle(idInst, citemname, 0); pxact->hDdeData = 0; pxact->wFmt = CF_TEXT; pxact->wType = XTYP_ADVSTART; // DDE Advice (dde automation link) if(!(pxact->ret = (DWORD) DdeClientTransaction( (LPBYTE)pxact->hDdeData, 0xFFFFFFFF, pxact->hConv, pxact->hszItem, pxact->wFmt, pxact->wType, pxact->ulTimeout, (LPDWORD)&pxact->Result))){ AfxMessageBox("Failed to DdeClientTransaction"); return true; } return false; } BOOL UdprocDdeAdviseStop(CString citemname){ if(pxact == NULL) return false; pxact->hszItem = DdeCreateStringHandle(idInst, citemname, 0); pxact->hDdeData = 0; pxact->wFmt = CF_TEXT; pxact->wType = XTYP_ADVSTOP; // DDE Advice (dde automation link) if(!(pxact->ret = (DWORD) DdeClientTransaction( (LPBYTE)pxact->hDdeData, 0xFFFFFFFF, pxact->hConv, pxact->hszItem, pxact->wFmt, pxact->wType, pxact->ulTimeout, (LPDWORD)&pxact->Result))){ AfxMessageBox("Failed to DdeClientTransaction"); return true; } return false; }

Callback Handler
This Handler is called every time there is a change in the item value.
HDDEDATA CALLBACK UdprocDdeCallback(UINT wType, UINT wFmt, HCONV hConv, HSZ hsz1,HSZ hsz2, HDDEDATA hData, DWORD lData1, DWORD lData2) { PTSTR psz; DWORD cb; CString cstopic, csitem; switch (wType) { case XTYP_REGISTER: case XTYP_UNREGISTER: case XTYP_DISCONNECT: case XTYP_XACT_COMPLETE: break; case XTYP_ADVDATA: // GET Topic Name cb = (DWORD)DdeQueryString(idInst, hsz1, NULL, 0, 0) + 1; psz = (PTSTR)malloc(cb * sizeof(TCHAR)); DdeQueryString(idInst, hsz1, psz, cb, 0); //ex)psz="PLC1" cstopic = psz; free(psz); // GET Item Name cb = (DWORD)DdeQueryString(idInst, hsz2, NULL, 0, 0) + 1; psz = (PTSTR)malloc(cb * sizeof(TCHAR)); DdeQueryString(idInst, hsz2, psz, cb, 0); //ex)psz="D0" csitem = psz; free(psz); if (!hData) hData = DdeClientTransaction(NULL, 0L, hConv, hsz2, wFmt, XTYP_REQUEST, 1000, NULL); if (hData) { #define MAXCCH 1024 cb = DdeGetData(hData, NULL, 0, 0); if (!hData || !cb) break; if (cb > MAXCCH) { // possibly HUGE object psz = (PTSTR)malloc(MAXCCH*sizeof(TCHAR)); DdeGetData(hData, (PBYTE)psz, (MAXCCH - 46) * sizeof(TCHAR), 0L); wsprintf(&psz[MAXCCH - 46], TEXT("Size=%ld"), cb); } else { psz = (PTSTR)malloc(cb * sizeof(TCHAR)); DdeGetData(hData, (LPBYTE)psz, cb, 0L); } pDlg->UpdateReadValue(psz); free(psz); DdeFreeDataHandle(hData); } return((HDDEDATA)DDE_FACK); break; } return 0; }

DDE Terminate
Terminate the connection to DAServer
BOOL UdprocDdeDisConnect(void) { if(pxact == NULL) return false; // Close DDE connection if(!DdeDisconnect(pxact->hConv)){ AfxMessageBox("Failed to DdeDisconnect"); return true; } if(pxact->ret){ DdeFreeDataHandle((HDDEDATA)pxact->ret); pxact->ret = 0L; } free(pxact); pxact = NULL; return false; }

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