Any update on this issue?
Aside: why is it necessary to have a "client" on the remote machine to access the USB port on the DNS-323? What prevents installing software on the 323 that presents the port as an attached Volume similar to the internal drives?
Shareport does not exist to allow a USB drive to be shared - it exists to allow a USB port to be shared - like any other "sharing" this requires a server process (which runs on the system with the resource to be shared) to make the share available, and a client process (which runs on the system that will use the shared resource) to access the server process.
Shareport may be used with USB drives, but can also be used with other USB devices - scanners, cameras, printers, etc.
Many people do not realise that ALL sharing requires this client/server approach because the functionality for the most common shares (disks & printers) is built into today's operating systems, and is now taken for granted, but this was not always so.