@aowoo said in How to access IO port in QT?: directly read and write to the I/O port AFAIK, It's impossible for Windows && Linux: On Windows you need in a special driver (It is not enough to use just some DLL's, because you need in a driver. Most likelly, that inpout32.dll has a pre-compiled driver in own resources and loads this driver in runtime). On Linux you need in a special permissions too.