WinAPI COM Port Communication

#include <iostream>
#include <cstdio>
#include "windows.h"

using namespace std;

int main() {
    //create handle to COM-Port
    const char *port = "COM3";
    HANDLE handle = CreateFile(port, GENERIC_ALL, 0, NULL, OPEN_EXISTING, 0, NULL);
    if (handle == INVALID_HANDLE_VALUE) {
        return -1;
    }

    //set baud rate to 9600
    DCB configuration;
    DWORD baudrate = CBR_9600;
    if (!GetCommState(handle, &configuration)) {
        return -1;
    }
    configuration.BaudRate = baudrate;
    if (!SetCommState(handle, &configuration)) {
        return -1;
    }

    //read as long as data is available
    char buffer;
    DWORD bytesRead = 0;
    DWORD bytesWritten = 0;
    while (ReadFile(handle, &buffer, 1, &bytesRead, 0)) {
        cout << buffer;
        //write every character back to the device
        if (!WriteFile(handle, &buffer, 1, &bytesWritten, 0)) {
            return -1;
        }
    }
}