This paper considers point-To-point wireless communications where an energy-constrained node, which has insufficient energy for data transmission, wants to exchange messages with a node with enough energy. In this system, we study power splitting (PS) based energy cooperation methods by exploiting wireless energy transfer techniques and propose a new concept called sustainable wireless information and power exchange (SWIPE). In this SWIPE protocol, the node which has sufficient energy first transmits the information signal to the energy-constrained node. Then, the received signal at the energy-constrained node is utilized for both information decoding and energy harvesting via a PS circuit. At the consecutive time slot, by using the harvested energy, the energy-constrained node is now able to send a signal to the other node which employs a similar PS technique. This procedure continues by switching the operations of two nodes at each time slot. For the proposed SWIPE protocol, we present the optimal PS ratio computation algorithm in order to maximize the weighted sum throughput performance. Simulation results confirm the efficacy of the proposed SWIPE protocol over conventional schemes.