Important note. If I start a software with +ntdll debug option than every reading from serial port produces such log: Code: trace:file:ReadFile 0xdc 0x32e734 1 0x32e694 (nil) trace:ntdll:NtReadFile (0xdc,(nil),(nil),(nil),0x32e634,0x32e734,0x00000001,(nil),(nil)),partial stub! trace:ntdll:NtReadFile = SUCCESS (1) trace:ntdll:NtDeviceIoControlFile (0xdc,(nil),(nil),(nil),0x32e5e4,0x001b006c,(nil),0x00000000,0x32e63c,0x00000014) trace:comm:io_control 0xdc IOCTL_SERIAL_GET_COMMSTATUS (nil) 0 0x32e63c 20 0x32e5e4 What does a "partial stub!" means?