Anyone interested in controlling the serial ports directly via kernel32 functions? You need the following file "cfx.ini" with the settings of the used comm port [Comm] CommPort=1 CommBaud=9600 CommParity=0;0=none, 1=odd, 2=even, 3=mark, 4=space CommBits=8;4-8 CommStop=1;0=0, 1=1,5, 2=2 CommCtrl=0x0011 LogDir="" Debug=1 I spent much time to find an alternative to mscomm32 or other udfs using a dll. The test script sends a reset to a modem and shows the response. Sending chr(0) is p