No, you're quite right, that version of upgclient is hosed, even on real serial ports. I wonder how we managed that!

Fortuitously, it turns out I do still have an older version installed on a machine here. I've tested it (on /dev/ttyS1 no less) and it does work. It doesn't report a version number, but note that it should be 441,024 bytes long as opposed to the 453,828 bytes of the v3alpha1 release.

Peter