On page 323 where you play with TXT record there is a message -indexOfObjectIdenticalTo: sent to an array object. It is array of net services and on page 321 when you need to get a reference to an object from the same array you just use more familiar -indexOfObject: so I went and looked it up in the documentation and I still have no idea if these two methods are effectively the same or not, at least with arrays.
“-indexOfObjectIdenticalTo: - Objects are considered identical if their object addresses are the same.”
"-indexOfObject: - Objects are considered equal if isEqual: returns YES."
Did you use it just to make us aware of it or is there another reason?
Plus, a minor detail on page 324, method name is -netServiceDidResloveAddress:, but in text you refer to it as -netServiceDidReslove: