USB COM12 (Win11 Host) --> COM1 (Win98 Guest) fails

[KedalionDaimon]

So, I am having a USB Serial port on the Windows 11 Host machine, showing up as "COM12" both in the Device Manager and in Powershell.

On VirtualBox 7.0.14, I am having a Windows 98 Guest. For this Guest, the USB ports are NOT enabled, i.e. under Enable Host Controller, the box is off, to avoid interference.

In the Settings, Serial Ports interface, "Enable Serial Ports" is on for the Device "COM1", IRQ 4, I/O Port 0x3F8.

"Port Mode: Host Device" is selected. "Path/Address" is set to COM12 (having experimented with and without colon).

When trying to boot up, I get the following error message:

"VM Name: Win98

Failed to open host device 'COM12' (VERR_INVALID_HANDLE).
Result Code:
E_FAIL (0X80004005)
Component:
ConsoleWrap
Interface:
IConsole {6ac83d89-6ee7-4e33-8ae6-b257b2e81be8}"

To note: if I set the Mode to TCP, and set there a port, I CAN connect to Windows 98's COM1: serial port over telnet. So this is not an issue with the Guest, but clearly so with the Host. Please advise how I can channel the Guest's COM1: serial port to the Host's COM12: USB serial device. Thank you.

EDIT: The VM does not start from the command line, either (tried with COM12 and COM12: - same result) :

C:\Program Files\Oracle\VirtualBox>VBoxManage modifyvm Win98 --uartmode1 COM12:

C:\Program Files\Oracle\VirtualBox>VBoxManage startvm Win98
Waiting for VM "Win98" to power on...
VBoxManage.exe: error: Failed to open host device 'COM12:' (VERR_INVALID_HANDLE)
VBoxManage.exe: error: Details: code E_FAIL (0x80004005), component ConsoleWrap, interface IConsole

[jorgensen]

Windows 98 only has the option of COM1 to COM7 as I recall.
If you absolute need to use the COM12 as COM1 in Windows 98 guest you need to manual control Port and IRQ assignment.
I can recommend the rather old below link for the XP procedure to control port setting etc.
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