Memantau Peristiwa Komunikasi

Contoh kode berikut membuka port serial untuk I/O yang tumpang tindih, membuat masker peristiwa untuk memantau sinyal CTS dan DSR, lalu menunggu peristiwa terjadi. Fungsi WaitCommEvent harus dijalankan sebagai operasi yang tumpang tindih sehingga alur proses lainnya dapat melakukan operasi I/O selama penantian.

C++

#include <windows.h>
#include <tchar.h>
#include <assert.h>
#include <stdio.h>

void _tmain(
            int argc, 
            TCHAR *argv[]
           )
{
    HANDLE hCom;
    OVERLAPPED o;
    BOOL fSuccess;
    DWORD dwEvtMask;

    hCom = CreateFile( TEXT("\\\\.\\COM1"),
        GENERIC_READ | GENERIC_WRITE,
        0,    // exclusive access 
        NULL, // default security attributes 
        OPEN_EXISTING,
        FILE_FLAG_OVERLAPPED,
        NULL 
        );

    if (hCom == INVALID_HANDLE_VALUE) 
    {
        // Handle the error. 
        printf("CreateFile failed with error %d.\n", GetLastError());
        return;
    }

    // Set the event mask. 

    fSuccess = SetCommMask(hCom, EV_CTS | EV_DSR);

    if (!fSuccess) 
    {
        // Handle the error. 
        printf("SetCommMask failed with error %d.\n", GetLastError());
        return;
    }

    // Create an event object for use by WaitCommEvent. 

    o.hEvent = CreateEvent(
        NULL,   // default security attributes 
        TRUE,   // manual-reset event 
        FALSE,  // not signaled 
        NULL    // no name
         );
    

    // Initialize the rest of the OVERLAPPED structure to zero.
    o.Internal = 0;
    o.InternalHigh = 0;
    o.Offset = 0;
    o.OffsetHigh = 0;

    assert(o.hEvent);

    if (WaitCommEvent(hCom, &dwEvtMask, &o)) 
    {
        if (dwEvtMask & EV_DSR) 
        {
             // To do.
        }

        if (dwEvtMask & EV_CTS) 
        {
            // To do. 
        }
    }
    else
    {
        DWORD dwRet = GetLastError();
        if( ERROR_IO_PENDING == dwRet)
        {
            printf("I/O is pending...\n");

            // To do.
        }
        else 
            printf("Wait failed with error %d.\n", GetLastError());
    }
}