I don't see this is as a problem.  ServerBase is only used ever used as a parent class of Server.  In addition, Server has to call its constructor with a property that was added by SocketBase, which seems to indicate that it isn't really supposed to be a standalone, concrete class.  Adding in the introspection features to ServerBase doesn't seem like a good idea since it would just replicate the functionality in Server.  There is probably a better way to divide functionality between ServerBase and Server that could make ServerBase useful on its own though.