//+---------------------------------------------------------------------------
//
//  function:   DeviceReceiveThread
//
//  Synopsis:   Thread to watch for an incoming fax transmission
//
//  Arguments:  [pdwDeviceId] - pointer to the virtual fax device identifier
//
//  Returns:    DWORD
//
//----------------------------------------------------------------------------
DWORD WINAPI DeviceReceiveThread(LPDWORD pdwDeviceId)       
{
        // hChangeNotification is a handle to a notification change in a directory
        HANDLE         hChangeNotification;
        // hWaitObjects are the handles to the wait objects
        HANDLE         hWaitObjects[2];
        // dwDeviceId is the virtual fax device identifier
        DWORD          dwDeviceId;
        // pLineMessage is a pointer to LINEMESSAGE structure to signal an incoming fax transmission to the fax service
        LPLINEMESSAGE  pLineMessage;

        //WriteDebugString(L"---SampleFSP: DeviceReceiveThread Enter---\r\n");

        // Copy the virtual fax device identifier
        dwDeviceId = *pdwDeviceId;
        MemFreeMacro(pdwDeviceId);
		WriteDebugString(L"---SampleFSP: DeviceReceiveThread (Device=%x) Enter---\r\n", dwDeviceId);

        // Create the change notification handle
        hChangeNotification = FindFirstChangeNotification(g_pDeviceInfo[dwDeviceId]->Directory,
                        FALSE, 
                        FILE_NOTIFY_CHANGE_ATTRIBUTES);
        if (hChangeNotification == INVALID_HANDLE_VALUE) {
                goto Exit;
        }

        // Wait for access to this virtual fax device
        EnterCriticalSection(&g_pDeviceInfo[dwDeviceId]->cs);

        // Set hWaitObjects
        hWaitObjects[0] = g_pDeviceInfo[dwDeviceId]->ExitEvent;
        hWaitObjects[1] = hChangeNotification;

        // Release access to this virtual fax device
        LeaveCriticalSection(&g_pDeviceInfo[dwDeviceId]->cs);

        while (TRUE) {
                // Wait for the exit event or notification change to be signaled
                if ( WaitForMultipleObjects(2,
                                        hWaitObjects,
                                        FALSE,
                                        INFINITE) == WAIT_OBJECT_0) {
                        break;
                }

                // Wait for access to this virtual fax device
                EnterCriticalSection(&g_pDeviceInfo[dwDeviceId]->cs);

                if (g_pDeviceInfo[dwDeviceId]->Status == DEVICE_IDLE) {
                        // Allocate a block of memory for the completion packet
                        pLineMessage = (LPLINEMESSAGE) LocalAlloc(LPTR, sizeof(LINEMESSAGE));
                        if (pLineMessage != NULL) {
                                // Initialize the completion packet
                                // Set the completion packet's handle to the virtual fax device
                                pLineMessage->hDevice = dwDeviceId + NEWFSP_DEVICE_ID_PREFIX;
                                // Set the completion packet's virtual fax device message
                                pLineMessage->dwMessageID = 0;
                                // Set the completion packet's instance data
                                pLineMessage->dwCallbackInstance = 0;
                                // Set the completion packet's first parameter
                                pLineMessage->dwParam1 = LINEDEVSTATE_RINGING;
                                // Set the completion packet's second parameter
                                pLineMessage->dwParam2 = 0;
                                // Set the completion packet's third parameter
                                pLineMessage->dwParam3 = 0;

								WriteDebugString(L"---SampleFSP: DeviceReceiveThread (Device=%x) Signaling Fax Service...---\r\n", dwDeviceId);

                                // Post the completion packet
                                PostQueuedCompletionStatus(g_CompletionPort, 
                                                sizeof(LINEMESSAGE),
                                                g_CompletionKey,
                                                (LPOVERLAPPED) pLineMessage);
                        }
                }

                // Release access to this virtual fax device
                LeaveCriticalSection(&g_pDeviceInfo[dwDeviceId]->cs);

                // Find the next notification change
                FindNextChangeNotification(hChangeNotification);
        }

Exit:
        if (hChangeNotification != INVALID_HANDLE_VALUE) {
                // Close the handle to the change notification
                FindCloseChangeNotification(hChangeNotification);
        }

        // Close the handle to the exit event
        CloseHandle(hWaitObjects[0]);

        //WriteDebugString(L"---SampleFSP: DeviceReceiveThread Exit---\r\n");
		WriteDebugString(L"---SampleFSP: DeviceReceiveThread (Device=%x) Exit---\r\n", dwDeviceId);

        return 0;
}

 Private Sub ButtonStartMailSlotEvent_Click(sender As Object, e As EventArgs) Handles ButtonStartMailSlotEvent.Click
    MakeMailSlot("\\.\mailslot\mstest", True, True)
    Dim SA As SECURITY_ATTRIBUTES
    Dim hEvent As IntPtr = CreateEvent(SA, False, False, vbNullString) 'autoreset,non-signaled state
    Dim ov As OVERLAPPED
    ov.hEvent = hEvent
    Dim lBufferSize As Integer = 260 ' arbitrary - can be set higher/lower if desired
    Dim sBuffer(lBufferSize - 1) As Byte
    Dim lBytesRead As Integer 'сколько байт прочитали -чтоб обрезать буфер
    Dim rc As Integer
    rc = ReadFileOv(hMailSlotHandle, sBuffer, lBufferSize, 0, ov)
    Do
      ' wait for signal
      WaitForSingleObject(hEvent, INFINITE)
      If GetOverlappedResult(hMailSlotHandle, ov, lBytesRead, False) = False Then
        If Err.LastDllError = ERROR_INSUFFICIENT_BUFFER Then
          GetMailslotInfo(hMailSlotHandle, 0, lBufferSize, 0, 0) 'получаем точный размер буфера, если не хватило
          ReDim sBuffer(lBufferSize - 1)
          'читаем повторно с точным размером буфера
          If ReadFile(hMailSlotHandle, sBuffer, lBufferSize, lBytesRead, IntPtr.Zero) = False Then
            Exit Do 'хз-не должно такого быть
          End If
        Else
          Exit Do 'любая другая ошибка, например при обращении к несуществующему MailSlot
        End If
      Else 'в случае успеха с первого раза буфер надо обрезать
        ReDim Preserve sBuffer(lBytesRead - 1)
      End If
      Using mstream As New IO.MemoryStream(sBuffer)
        Using reader As New IO.StreamReader(mstream, System.Text.Encoding.Default, True)
          Debug.Print("'" & reader.ReadToEnd() & "'")
        End Using
      End Using
      'переинициалиация
      ov.Internal = IntPtr.Zero : ov.InternalHigh = IntPtr.Zero : ov.Offset = 0 : ov.OffsetHigh = 0 : ov.hEvent = hEvent
      lBufferSize = 260
      ReDim sBuffer(lBufferSize - 1)
      rc = ReadFileOv(hMailSlotHandle, sBuffer, lBufferSize, 0, ov)
    Loop

    '------
    CloseMailSlot()
  End Sub

01.26.2017@18:33:42.070:
---SampleFSP: DeviceReceiveThread (Device=0) Enter---
01.26.2017@18:33:42.070:
   Mailslot \\.\mailslot\MailSlotMyFSPWaitLine0 created successfully.
01.26.2017@18:34:30.979:
---SampleFSP: fnFaxLineCallback Enter---
01.26.2017@18:34:30.979:
   Device=0;Receive=0;Send=1
01.26.2017@18:34:30.979:
---SampleFSP: fnFaxLineCallback Exit---
01.26.2017@18:34:30.979:
   Mailslot \\.\mailslot\MailSlotMyFSPWaitLine0 deleted.
01.26.2017@18:34:30.979:
---SampleFSP: DeviceReceiveThread (Device=0) Exit---
01.26.2017@18:34:35.195:
---SampleFSP: fnFaxLineCallback Enter---
01.26.2017@18:34:35.195:
   Device=0;Receive=1;Send=1
01.26.2017@18:34:35.195:
---SampleFSP: fnFaxLineCallback Exit---
01.26.2017@18:34:35.195:
---SampleFSP: DeviceReceiveThread (Device=0) Enter---
01.26.2017@18:34:35.195:
   Mailslot \\.\mailslot\MailSlotMyFSPWaitLine0 created successfully.
01.26.2017@18:35:40.856:
   Message 'Incoming Call' received.
01.26.2017@18:35:40.856:
---SampleFSP: DeviceReceiveThread (Device=0) Signaling Fax Service...---
01.26.2017@18:35:40.856:
---SampleFSP: FaxDevStartJob (Device=0) Enter---
01.26.2017@18:35:40.856:
---SampleFSP: FaxDevStartJob (Device=0) Exit---
01.26.2017@18:35:40.856:
---SampleFSP: FaxDevReceive Enter---
01.26.2017@18:35:40.856:
   CallHandle                 : 0x00000000
...

#include "stdafx.h"

wchar_t const * slotName = L"\\\\.\\mailslot\\mstest";
int const bufSize = 1024;
BOOL WINAPI consoleHandler(DWORD ctrlType) {
	if (ctrlType == CTRL_C_EVENT) {
		HANDLE hFile = CreateFile(slotName, GENERIC_WRITE, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
		DWORD sz = 0;
		int rc = WriteFile(hFile, "MSG", 3, &sz, 0);
		CloseHandle(hFile);
		return TRUE;
	}
	return FALSE;
}
int main()
{
	int rc;
	HANDLE hSlot = CreateMailslot(slotName, bufSize, MAILSLOT_WAIT_FOREVER, NULL);
	HANDLE hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
	rc = SetConsoleCtrlHandler(consoleHandler, TRUE);
	HANDLE hTimer = CreateWaitableTimer(NULL, TRUE, NULL);
	LARGE_INTEGER dueTime;
	dueTime.QuadPart = -20000000LL;
	rc = SetWaitableTimer(hTimer, &dueTime, 0, NULL, NULL, 0);
	char buf[bufSize + 1];
	OVERLAPPED ov = {};
	ov.hEvent = hEvent;
	rc = ReadFile(hSlot, buf, bufSize, 0, &ov);

	do {
		HANDLE events[2] = { hEvent,hTimer };
		rc = WaitForMultipleObjects(2, events, FALSE, INFINITE);
		if (rc == WAIT_FAILED) break;
		DWORD sz = 0;
		rc = GetOverlappedResult(hSlot, &ov, &sz, FALSE);
		if (rc) {
			buf[sz] = 0;
			printf("Message: %s\n", buf);
			ov = {};
			ov.hEvent = hEvent;
			rc = ReadFile(hSlot, buf, bufSize, 0, &ov);
			if (!rc && GetLastError() != ERROR_IO_PENDING) {
				break;
			}
		}
		else if (GetLastError() != ERROR_IO_INCOMPLETE) {
			break;
		}
		rc = WaitForSingleObject(hTimer, 0);
		if (rc==WAIT_OBJECT_0 ) {
			rc = SetWaitableTimer(hTimer, &dueTime, 0, NULL, NULL, 0);
			printf("Timer\n");
		}
		else if (rc != WAIT_TIMEOUT) {
			break;
		}
	} while (1);

	printf("Error: %i\n", GetLastError());

	return 0;
}