Thank You Ed for Your reply. Actually the problem is very old 386 machine attached to very rear peace of measurement hardvare, so I must do it under DOS.
I tried with "mode com", but no result. Under MSDN is one sampe how to read from COM port, but I did not work. Problem is, just like you said XON/XOFF and RTS/CTS. I dont know how to set those parameters from MsDOS 6.22 !
Baud rate, parity, stop bits and data bits I can set, but the rest ???
I don't hawe idea !

Thank You again !