Build a DDE Server

• 1). Open Visual C++ 6.0 and start a "New Project."
  
  
• 2). Click on "Win32Application" to select it as the project type, then name it "DdemlSvr." Select "An Empty Project" when asked for the type of project you want.
  
  
• 3). Add a file called "main.cpp." to your project.
  
  
• 4). Copy the following code:
  
  #include <windows.h>
  
  #include <stdio.h>
  
  #include <ddeml.h>
  
  // Globals...
  
  HSZ g_hszAppName;
  
  HSZ g_hszTopicName;
  
  HSZ g_hszItemName;
  
  int g_count = 0;
  
  DWORD g_idInst = 0;
  
  // Declarations:
  
  HDDEDATA EXPENTRY DdeCallback(UINT type, UINT fmt, HCONV hConv, HSZ hsz1, HSZ hsz2, HDDEDATA hData, DWORD dwData1, DWORD dwData2);
  
  // WinMain()..
  
  int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
  
  // Initialize DDEML...
  
  if(DdeInitialize(&g_idInst, DdeCallback, APPCLASS_STANDARD, 0)) {
  
  MessageBox(NULL, "DdeInitialize() failed", "Error", MB_SETFOREGROUND);
  
  return -1;
  
  }
  
  // Create string handles...
  
  g_hszAppName = DdeCreateStringHandle(g_idInst, "DdemlSvr", NULL);
  
  g_hszTopicName = DdeCreateStringHandle(g_idInst, "MyTopic", NULL);
  
  g_hszItemName = DdeCreateStringHandle(g_idInst, "MyItem", NULL);
  
  if( (g_hszAppName == 0) || (g_hszTopicName == 0) || (g_hszItemName == 0) ) {
  
  MessageBox(NULL, "DdeCreateStringHandle() failed", "Error", MB_SETFOREGROUND);
  
  return -2;
  
  }
  
  // Register DDE server
  
  if(!DdeNameService(g_idInst, g_hszAppName, NULL, DNS_REGISTER)) {
  
  MessageBox(NULL, "DdeNameService() failed!", "Error", MB_SETFOREGROUND);
  
  return -3;
  
  }
  
  // Create a timer to simulate changing data...
  
  SetTimer(0,0,1,0);
  
  // Message loop:
  
  MSG msg;
  
  while (GetMessage(&msg, NULL, 0, 0)) {
  
  // On WM_TIMER, change our counter, and update clients...
  
  if(msg.message == WM_TIMER) {
  
  g_count++;
  
  DdePostAdvise(g_idInst, g_hszTopicName, g_hszItemName);
  
  }
  
  TranslateMessage(&msg);
  
  DispatchMessage(&msg);
  
  }
  
  return msg.wParam;
  
  }
  
  // Our DDE Callback function...
  
  HDDEDATA EXPENTRY DdeCallback(UINT wType, UINT fmt, HCONV hConv, HSZ hsz1, HSZ hsz2, HDDEDATA hData, DWORD dwData1, DWORD dwData2) {
  
  switch (wType) {
  
  // ----------------------------------------------------------------
  
  case XTYP_CONNECT:
  
  // Client is trying to connect. Respond TRUE if we have what they want...
  
  if ((!DdeCmpStringHandles(hsz1, g_hszTopicName)) &&
  
  (!DdeCmpStringHandles(hsz2, g_hszAppName)))
  
  return (HDDEDATA)TRUE; // SERVER supports Topic|Service
  
  else
  
  return FALSE; // SERVER does not support Topic|Service
  
  // ----------------------------------------------------------------
  
  case XTYP_ADVSTART:
  
  // Client starting advisory loop.
  
  // Say "ok" if we have what they are asking for...
  
  if((!DdeCmpStringHandles(hsz1, g_hszTopicName)) &&
  
  (!DdeCmpStringHandles(hsz2, g_hszItemName)))
  
  return (HDDEDATA)TRUE; // SERVER supports Topic|Service
  
  else
  
  return FALSE; // SERVER does not support Topic|Service
  
  // ----------------------------------------------------------------
  
  case XTYP_ADVREQ:
  
  // Client wants our data. Since this is specific to Excel, we'll
  
  // go ahead and assume they want XlTable-formatted data. For a
  
  // generic DDE server, you might want to handle various formats
  
  // specified by the passed in fmt parameter.
  
  if(!DdeCmpStringHandles(hsz1, g_hszTopicName) &&
  
  !DdeCmpStringHandles(hsz2, g_hszItemName)) {
  
  short xltableData[100];
  
  // tdtTable record...
  
  xltableData[0] = 0x0010; // tdtTable
  
  xltableData[1] = 4; // 2 short ints following
  
  xltableData[2] = 1; // # rows
  
  xltableData[3] = 1; // # cols
  
  // tdtInt record...
  
  xltableData[4] = 0x0006;
  
  xltableData[5] = 2;
  
  xltableData[6] = (short)g_count;
  
  return DdeCreateDataHandle(g_idInst, (UCHAR*)xltableData, 2*7, 0, g_hszItemName, fmt, 0);
  
  }
  
  // ----------------------------------------------------------------
  
  default:
  
  return (HDDEDATA)NULL;
  
  }
  
  }
  
  
• 5). Paste the code into the file "main.cpp" that you created.
  
  
• 6). Compile and then start up the project.
  
  

Test Your Server

• 1). Press "Ctrl" + "Shift" + "Esc" to bring up the Windows Task Manager, then select the "Processes" tab.
  
  
• 2). Ensure that "DdemlSvr.exe" is one of the applications running on the list.
  
  
• 3). Start up Microsoft Office Excel and type "=DdemlSvr|MyTopic!MyItem" into a cell. The cell should now contain the increasing value of the g_count.
  
  

Use the Server Remotely

• 1). Run the "DdemlSvr.exe" in a Windows NT 4.0 machine that is networked. Then start "DdeShare" from the command line.
  
  
• 2). Click "Shares" from the menu that appears, then "DDE Shares," followed by "Add a Share."
  
  
• 3). Enter the following values under "Application Name":
  
  Share Name: MyShare$
  
  Old Style: DdemlSvr.DDE
  
  New Style: DdemlSvr.OLE
  
  Static: DdemlSvr
  
  
• 4). Enter "MyTopic" into the three boxes under "Topic Name." Select "OK."
  
  
• 5). Click on "MyShare$," then "Trust Share," then the "Initiate to Application Enable" checkbox. Select "OK" in all of the dialog boxes and then quit "DdeShare."
  
  
• 6). Run Excel on a different Windows NT 4.0 machine, but still on the same network.
  
  
• 7). Copy the following:
  
  ='\\SERVERNAME\NDDE$'|'MyShare$'!MyItem
  
  
• 8). Paste what you copied into a cell in Excel. Replace "SERVERNAME" with the name of your network server machine. You should see a rapidly increasing number in the cell.