ERROR_UNKNOWN_PORT 0x80070704

Error code 1796 · HRESULT 0x80070704

WINDOWS

The specified port is unknown.

Windows troubleshooting diagram: Device Manager warning and a system file scan
Windows errors: check drivers, system files and Event Viewer, in that order.

What it means

ERROR_UNKNOWN_PORT is a Windows error code (system error 1796, returned as HRESULT 0x80070704) reported by Windows. Its official message is: “The specified port is unknown.”

How to fix ERROR_UNKNOWN_PORT

  1. Reboot once — many one-off system codes disappear with a clean restart
  2. Repair system files: 'sfc /scannow' then 'DISM /Online /Cleanup-Image /RestoreHealth'
  3. Find the source in Event Viewer → System: filter for this exact code and open its provider link

Related errors

ERROR_PRINTER_DRIVER_ALREADY_INSTALLEDERROR_UNKNOWN_PRINTER_DRIVERERROR_REDIRECTOR_HAS_OPEN_HANDLESSTATUS_ACCESS_VIOLATIONSTATUS_IN_PAGE_ERRORSTATUS_ACCESS_DENIEDSTATUS_INVALID_IMAGE_FORMATSTATUS_STACK_OVERFLOW

Source: Microsoft WinError.h

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