Broadcast a message to multiple instances of an application

• Download demo - 4 Kb
• Download source - 13 Kb

Introduction

This application describes how to broadcast a message to multiple instance of an application using SendMessageNotify API.

Details

Follow the following steps to broadcast message :-

• Register the message function and get its id using RegisterWindowMessage API. This function will return a unique id for the message if the registration is success UINT WM_MYMESSAGE = RegisterWindowMessage("OnTestMyMessage");
• Add the message function in the message map using ON_REGISTERED_MESSAGE instead of ON_MESSAGE

  BEGIN_MESSAGE_MAP(CTestFindWindowDlg, CDialog)
   // Use ON_REGISTERED_MESSAGE macro instead of ON_MESSAGE
   ON_REGISTERED_MESSAGE(WM_MYMESSAGE,OnTestMyMessage)
  END_MESSAGE_MAP()

• Broadcast the message using ::SendNotifyMessage API

  BOOL a = ::SendNotifyMessage(HWND_BROADCAST, WM_MYMESSAGE,0,1000);

• Function declaration and definition

  // .h
  afx_msg void OnTestMyMessage(WPARAM wParam,LPARAM lParam);
  
  //.cpp
  void CTestFindWindowDlg::OnTestMyMessage(WPARAM wParam,LPARAM lParam)
  {
     int a  =(int)lParam;
     CString strValue;
     strValue.Format("%d",a);
     AfxMessageBox("Broadcast :"+strValue);
  }