Is it possible to broadcast messages in named pipe between a server and multiple clients?

Question

I am new to pipes and interprocess communication in windows. I want to use named pipe to communicate between processes. But in my case I should send message to multiple clients, so I want to check is it possible to send broadcast messages in named pipe communication. Thank you in advance.

Answer 1

This namedpipe client will broadcast 40 messages one message per second which will be received one of the multiple servers which are connected to same pipe.

NamedPipe Client

std::wcout << L"I am broadcasting messages!\n"; 
TCHAR                       chReadBuf[_MAX_PATH] = { 0 };
LPTSTR                      lpszWrite= TEXT("Default message from client");
DWORD                       cbRead = 0;
TCHAR                       szTempFolderPath[_MAX_PATH] = { 0 };
TCHAR                       aTempFileName[_MAX_PATH] = { 0 };

for (int i=0; i<40;i++)
{
    std::wcout<< lpszWrite << std::endl;

    CallNamedPipe(L"\\\\.\\pipe\\my_pipe", lpszWrite, (lstrlen(lpszWrite) + 1) * sizeof(TCHAR), chReadBuf, (_MAX_PATH * _MAX_PATH) * sizeof(TCHAR), &cbRead, NMPWAIT_WAIT_FOREVER);
Sleep(1000);
}

Create multiple namedpipe servers each server is using same pipe, which is used by namedpipe client to broadcast message.

NamedPipe Server

HANDLE      m_hPipe = nullptr;
m_hPipe = CreateNamedPipe(L"\\\\.\\pipe\\my_pipe", PIPE_ACCESS_DUPLEX, PIPE_TYPE_MESSAGE | PIPE_WAIT, PIPE_UNLIMITED_INSTANCES, MAX_PATH * MAX_PATH, MAX_PATH * MAX_PATH, 100000, NULL);
            
do {
        HRESULT             hr = S_OK;
        TCHAR       chReadBuf[MAX_PATH * MAX_PATH];
        BOOL        fSuccess = FALSE;
        DWORD       cbRead;

        ConnectNamedPipe(m_hPipe, NULL);
    
        fSuccess = ReadFile(
            m_hPipe,      // pipe handle 
            chReadBuf,  // buffer to receive reply 
            (MAX_PATH * MAX_PATH) * sizeof(TCHAR),  // size of buffer 
            &cbRead,  // number of bytes read 
            NULL);    // not overlapped 

        chReadBuf[cbRead] = '\0';
        std::wcout <<L"Received by Server 1" << chReadBuf << std::endl;

        DisconnectPipe();

    } while (1);

• Make note that all your servers should use same pipename as given in above code \\\\.\\pipe\\my_pipe
• Broadcasted message will be received by only one server at a time, out of multiple servers.