serial port doesn't work

[cracker84]

Hi, I'm using VirtualBox 4.26 on Windows 7, and the guest system is also Windows 7, in VirtualBox of the host machine I've set the serial port number to COM1, host mode is host device, port/file path is COM1:(I've tried COM1 as well), under the device manager, the host machine's serial port number is COM1/LPT1; and in the guest system, it automatically detects COM1/LPT1 in the device manager, I don't need to add legacy hardware(I've tried to add it, it created a COM3, and didn't give me the option to choose the COM port number, and it got a yellow warning mark), but when I tried to use the port, it has no respond at all, so can someone please help me, thank you.

[aeichner]

Please reopen if still relevant with a recent VirtualBox release.