public static extern int SetCommState(IntPtr hCommDev, ref DCB lpDCB);
public static extern int BuildCommDCBAndTimeouts(string lpDef, ref DCB lpDCB, ref COMMTIMEOUTS lpCommTimeouts);
public static extern int GetCommState(int nCid, ref DCB lpDCB);
public static extern int BuildCommDCB(string lpDef, ref DCB lpDCB);