Problem with Named event of length 4*n-1using CreateEvent() and Openevent() - multithreading

Question

I have two applications, one creates a named event using CreateEvent() and other opens the same event using OpenEvent(), as follows:
Application A.exe:
DLSRemoteConnnectionRqstEvent = CreateEvent(NULL, FALSE, FALSE, (LPCWSTR)DLS_REMOTE_CONNECTION_RQST_EVENT);
if (GetLastError() != 0)
{
DLSRemoteConnnectionRqstEvent = OpenEvent(EVENT_ALL_ACCESS, TRUE,(LPCWSTR)DLS_REMOTE_CONNECTION_RQST_EVENT);
}
else
{
cout<<"DLS_REMOTE_CONNECTION_RQST_EVENT created"<<endl;
}
Application B.exe :
DLSRemoteConnnectionRqstEvent =OpenEvent(EVENT_ALL_ACCESS, TRUE, (LPCWSTR)DLS_REMOTE_CONNECTION_RQST_EVENT);
if (GetLastError() != 0 && INVALID_HANDLE_VALUE == m_DLSRemoteConnnectionRqstEvent)
{
DLSRemoteConnnectionRqstEvent = CreateEvent(NULL, FALSE, FALSE, (LPCWSTR)DLS_REMOTE_CONNECTION_RQST_EVENT);
}
else
{
cout<<"m_DLSRemoteConnnectionRqstEvent opened"<<endl;
}
The event name is defined in a common header file as below:
#define CS_REMOTE_CONNECTION_RQST_EVENT "DLS_REMOTE_CONNECTION_RQST_MSG_TYPE"
Application A is able to create the event successfully, but Application B is not able to open the event, getting a handle value of NULL.
I have tested a few scenarios and came to know that if the event name is a length of 4n-1 then the open event always gives me a NULL handle value, and if the event name is less then 4n-1 or more than 4*n-1 then my application works fine.
Please help with why my application is behaving like this when the event name length is 4*n-1.
Other events created and opened in applications similarly as above are working fine as their lengths are not 4*n-1.
CreateEvent() and OpenEvent() should work on all the event lengths.

Answer 1

Your LPCWSTR typecasts are wrong. You can't cast narrow strings into wide strings like you are doing. Use a wide string literal to begin with, eg:
#define CS_REMOTE_CONNECTION_RQST_EVENT L"DLS_REMOTE_CONNECTION_RQST_MSG_TYPE"
...
CreateEventW(..., DLS_REMOTE_CONNECTION_RQST_EVENT);
...
OpenEventW(..., DLS_REMOTE_CONNECTION_RQST_EVENT);
That being said, using CreateEvent() and OpenEvent() the way you are is causing a race condition. Since it is clear that either application can create the event if it doesn't already exist, you should just use CreateEvent() in both applications and let it avoid the race condition for you. There is no reason to use OpenEvent() in this code at all.
Also, your error checking is wrong. Application A is not checking that a failure actually occurred before looking for a failure error code. CreateEvent() can report non-zero error codes in both success and failure conditions. Application B is at least trying to check if OpenEvent() failed, but it is doing so incorrectly since OpenEvent() returns NULL on failure, not INVALID_HANDLE_VALUE.
Try this instead:
Application A.exe and B.exe:
#define CS_REMOTE_CONNECTION_RQST_EVENT L"DLS_REMOTE_CONNECTION_RQST_MSG_TYPE"
...
DLSRemoteConnnectionRqstEvent = CreateEventW(NULL, FALSE, FALSE, DLS_REMOTE_CONNECTION_RQST_EVENT);
if (NULL == DLSRemoteConnnectionRqstEvent)
{
// error handling...
}
else
{
if (GetLastError() == ERROR_ALREADY_EXISTS)
cout << "DLS_REMOTE_CONNECTION_RQST_EVENT opened" << endl;
else
cout << "DLS_REMOTE_CONNECTION_RQST_EVENT created" << endl;
}