User applications, such as VoIP, have problems traversing NAT gateways or firewalls. To mitigate these problems, applications send keepalive messages through the gateways. The interval of sending keepalives is often unnecessarily short, which increases the network load, especially in mobile networks. Port Control Protocol (PCP) allows the applications to traverse the gateways and to optimize the interval. This paper describes the deployment of PCP in software-defined networks (SDN) and proposes a method to measure keepalive traffic reduction in mobile networks using PCP. The proposed solution extends the battery life of mobile devices and reduces the traffic overhead in WCDMA networks.