Eliot, in RSqueak we only implement exactly those primitives you need to run an update. If you check https://github.com/HPI-SWA-Lab/RSqueak/blob/master/rsqueakvm/plugins/socket_plugin.py there are only 13 primitive functions that do not simply print "Missing primitive". Those are all you need.
That's a rather long list of primitives.
Most images only use the resolver primitives, and optionally the TCP
primitives. If it's a Squeak image and useOldNetwork is enabled, then you
don't have to implement the new network primitives either.
Levente