c++ cant transfer data through com port when hyperterminal is connected - c++

Question

I am trying to make RS-232 communication between the PC and the PC MCU PIC. So I started making the PC program first in C++, and it was errorless, and according to the cout I made to output the status it should be working, but I wanted to be sure. So I downloaded Hyperterminal and connected Tx to Rx pin in serial com port, but whenever I try to connect the hyperterminal it gives an error, saying access denied (error 5) when I try to run my C++ program. I don't understand where the problem really is. Here's the full code, if the problem was the code's, just to make sure:
main.c:
#include <windows.h>
#include <winbase.h>
#include <iostream>
PDWORD sent;
char buf;
int main(){
DCB serial;
HANDLE hserial = CreateFile("\\\\.\\COM1", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
serial.DCBlength = sizeof(DCB);
serial.BaudRate = CBR_9600;
serial.fBinary = true;
serial.fParity = false;
serial.ByteSize = 8;
serial.Parity = NOPARITY;
serial.StopBits = ONESTOPBIT;
char result = BuildCommDCB("baud=9600 parity=N data=8 stop=1", &serial);
if(result != 0){
std::cout << "DCB Structure Successfully Created!" << std::endl;
}else{
std::cout << "DCB Structure Creation Failed!" << std::endl;
}
if(hserial != INVALID_HANDLE_VALUE){
std::cout << "COM Port Handle Successfully Created!" << std::endl;
}else{
std::cout << "COM Port Handle Creation Failed!" << std::endl;
std::cout << GetLastError() << std::endl;
}
char res = WriteFile(hserial, "0xFF", 1, sent, NULL);
if(res != 0){
std::cout << "Writing to COM Port Successfull!" << std::endl;
}else{
std::cout << "Writing to COM Port Failed!" << std::endl;
std::cout << GetLastError() << std::endl;
}
CloseHandle(&hserial);
return 0;
}

Answer 1

Only one program at a time can open a particular COM port. You can do your test if you have two COM ports available.