Named Pipe communication between service and application - c

Question

So I have a service which starts at boot time, and I have an application which I have placed in the startup folder.
So the client sometimes connects very late to the server of the named pipe.
Here is my code in my service.
hPipe = CreateNamedPipe(TEXT("\\\\.\\pipe\\popupPipe"),
PIPE_ACCESS_DUPLEX | PIPE_TYPE_BYTE | PIPE_READMODE_BYTE, // FILE_FLAG_FIRST_PIPE_INSTANCE is not needed but forces CreateNamedPipe(..) to fail if the pipe already exists...
PIPE_WAIT,
1, 1024 * 16, 1024 * 16,
NMPWAIT_USE_DEFAULT_WAIT,
NULL);
HRESULT
SendMessage(){
if (ConnectNamedPipe(hPipe, NULL) != FALSE) { // wait for someone to connect to the pipe
WriteFile(hPipe, (char *)message->buffer, sizeof(message->buffer), &dwWritten, NULL);
return S_OK;
}
return E_FAIL;
}
and here is the application
hPipe = CreateFile(TEXT("\\\\.\\pipe\\popupPipe"),
GENERIC_READ | GENERIC_WRITE,
0,
NULL,
OPEN_EXISTING,
0,
NULL);
if (hPipe == INVALID_HANDLE_VALUE)
return -1;
while (hPipe != INVALID_HANDLE_VALUE)
{
DWORD dwRead;
char buffer[100] = { 0 };
while (ReadFile(hPipe, buffer, sizeof(buffer), &dwRead, NULL) != FALSE);
if (dwRead == sizeof(buffer)) {
dwRead = 0;
buffer[100] = '\0';
temp = &buffer[1];
DisplayPopup(hInstance, cmdShow);
}
}
return 0;
but at the clients end the application always returns INVALID_HANDLE_VALUE
In the service SendMessage is called multiple times so even if it fails the first times it should succeed when the client connects shouldn't it.

Answer 1

You don't check if the creation of the pipe suceeds. Looking at the Microsoft documentation, it probably does not succeed because you mix parameters:
hPipe = CreateNamedPipe(TEXT("\\\\.\\pipe\\popupPipe"),
PIPE_ACCESS_DUPLEX | PIPE_TYPE_BYTE | PIPE_READMODE_BYTE, // FILE_FLAG_FIRST_PIPE_INSTANCE is not needed but forces CreateNamedPipe(..) to fail if the pipe already exists...
PIPE_WAIT,
1, 1024 * 16, 1024 * 16,
NMPWAIT_USE_DEFAULT_WAIT,
NULL);
should be:
hPipe = CreateNamedPipe(TEXT("\\\\.\\pipe\\popupPipe"),
PIPE_ACCESS_DUPLEX, // FILE_FLAG_FIRST_PIPE_INSTANCE is not needed but forces CreateNamedPipe(..) to fail if the pipe already exists...
PIPE_TYPE_BYTE | PIPE_READMODE_BYTE | PIPE_WAIT,
1, 1024 * 16, 1024 * 16,
NMPWAIT_USE_DEFAULT_WAIT,
NULL);