@Behrouz-AKT I think you have the wrong version of the DuetWiFiSocketServer project in your workspace. You don't need to build that project but you do need the correct version of the MessageFormats.h file in that project.
@meeloo it was an unfortunate breaking change when switching over from dozuki. The page names from the dozuki links are mostly still intact though, so a quick topic search on the new documentation should get you to the same place.
@dc42 Thanks. even one 6HC is an overkill for my project. I was initially looking at 3HC and running some steppers in series. Then I realized that main boards can be made slaves and the Mini 5 is a great option for additional drives and it has the WIFI too. I think the project will end as two Mini 5 brds when all is done. Thanks.