READ SERIAL PORT AND OPEN FILE,READ FROM SERIAL PORT (COM4) and open the file

My task should be simple, I have a qr code scanner device plugin COM4. I have tried to follow the example posted but not working. I need to scan the code embedded with the file path and unity to open that file (pdf file). Please help,Hi, I have a hardware QRcode scanner plugin COM4, I need to read in a file path from the qrcode and open that file. Can anyone help?