[MSVC]MFCで作られたDDEサーバに二回以上コネクトできない

対処方法

例

  //mainfrm.h
  class CMainFrame : public CMDIFrameWnd
  {
  //省略
  protected:
      afx_msg LRESULT OnDDEInitiate(WPARAM wParam, LPARAM lParam);
  }
  //mainfrm.cpp
  BEGIN_MESSAGE_MAP(CMainFrame, CMDIFrameWnd)
      //{{AFX_MSG_MAP(CMainFrame)
      //}}AFX_MSG_MAP
      ON_MESSAGE(WM_DDE_INITIATE, OnDDEInitiate)
  END_MESSAGE_MAP()
  LRESULT CMainFrame::OnDDEInitiate(WPARAM wParam, LPARAM lParam)
  {
      CWinApp* pApp = AfxGetApp();
      if (LOWORD(lParam) != 0 && HIWORD(lParam) != 0 &&
        (ATOM)LOWORD(lParam) == pApp->m_atomApp &&
        (ATOM)HIWORD(lParam) == pApp->m_atomSystemTopic)
      {
      // 重複するアトムを作成
          char szAtomName[_MAX_PATH];
          VERIFY(GlobalGetAtomName(pApp->m_atomApp,
              szAtomName, sizeof szAtomName) != 0);
          VERIFY(GlobalAddAtom(szAtomName) == pApp->m_atomApp);
          VERIFY(GlobalGetAtomName(pApp->m_atomSystemTopic,
              szAtomName, sizeof szAtomName) != 0);
          VERIFY(GlobalAddAtom(szAtomName) == pApp->m_atomSystemTopic);
          // WM_DDE_ACK を送る（呼出側が重複したアトムを削除）
          ::SendMessage((HWND)wParam, WM_DDE_ACK, (WPARAM)m_hWnd,
              MAKELPARAM(pApp->m_atomApp, pApp->m_atomSystemTopic));
      }
      return 0L;
  }