Asking Eric: I have the feeling our friend only likes us for our pool. What should I say to him?

Dear Eric: I am the older partner in a gay relationship. We have a mutual friend (John) who we have invited to our home four times for a swim and dinner. He has never invited us to his home to reciprocate for dinner, has never brought a bottle of wine or any gift of appreciation, has never sent us a thank you note or email, and never brings a towel for his use at the pool.