Circuit,
Circuit Diagram

Video:
Video

#ifndef __UNICODE__
#define __UNICODE__
#endif
#ifndef UNICODE
#define UNICODE
#endif
#ifndef _UNICODE
#define _UNICODE
#endif
#include <windows.h>
#include <stdio.h>

TCHAR * serial_port = L"COM2";

void BlinkLED(HANDLE hfile)
{
  while(TRUE){
    EscapeCommFunction(hfile,SETRTS);
    sleep(1);
    EscapeCommFunction(hfile,CLRRTS);
    sleep(1);
  }
}

int main(int argc,char** argv)
{
  HANDLE hfile = CreateFile(serial_port ,GENERIC_READ |GENERIC_WRITE ,\
                            0,
							0,
							OPEN_EXISTING,
							FILE_ATTRIBUTE_NORMAL,
							0);
	if (hfile==INVALID_HANDLE_VALUE)
	{
	  MessageBox(NULL,TEXT("Serial Port Does not Exist!"),TEXT("LED ON"),NULL);
	  exit(0);
	 }
	 
	 BlinkLED(hfile);
	 
	 CloseHandle(hfile);
}