Also, both Simple Server and Client render on the main thread with, so you can’t really rely on that for looking at hiccups and determining the cause. Main thread / runloop issues will interrupt rendering for both (just hold a menu down). It.. Is “simple” for a reason – just a fairly straight forward implementation.
Try loading a composition up with QCPlayer.app (Developer example that uses CVDisplayLink to drive rendering), you should see much fewer hiccups.