Asynchronous readfile returning ERROR_INVALID_HANDLE

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C

Windows

Trying to do asynchronous I/O on a device. My problem is ReadFile returns ERROR_INVALID_HANDLE.

I believe both Handle and OVERLAPPED hEvent are initialized so would very much appreciate it if someone could tell me what I'm doing wrong.

What I called a device is the Windows driver sample ndisprot which is a NDIS protocol driver.

What I have tried:

I have synchronous I/O and asynchronous I/O using ReadFileEx/WriteFileEx working.

This is the code I'm using:

HANDLE Handle = CreateFileA(
    ndisprot630,
    GENERIC_READ | GENERIC_WRITE,
    0,
    NULL,
    OPEN_EXISTING,
    FILE_FLAG_OVERLAPPED,
    NULL
);
if (Handle == INVALID_HANDLE_VALUE)
{
    DEBUGP("CreateFile failed, error 0x%x\n", GetLastError());
    return(INVALID_HANDLE_VALUE);
}

OVERLAPPED ol = { 0 };
ol.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
char buf[1500];

if (!ReadFile(Handle, buf, sizeof(buf), NULL, &ol))
{
    if (GetLastError() != ERROR_IO_PENDING)
    {
        DEBUGP("Error starting ReadFile 0x%x\n", GetLastError());
    }
}