C++ – Simple Reliable UDP C++ Libraries

Stack allocation is much faster since all it really does is move the stack pointer. Using memory pools, you can get comparable performance out of heap allocation, but that comes with a slight added complexity and its own headaches.

Also, stack vs. heap is not only a performance consideration; it also tells you a lot about the expected lifetime of objects.

Have a look at Kryo and its associated communication library KryoNet.

It's designed for exactly this kind of application (high performance network transport). I'm not sure if there is an Objective-C binding yet but even if there isn't it is well worth a look just to see how well the framework is designed.