The Internet of Things (IoT) will connect billions of devices deployed around the world in a near future by embedding mobile network and processing power capabilities into a wide range of physical computing devices used in everyday life of many people. Recent studies concerning IoT have addressed not only the interoperability of devices, but also the context awareness feature which makes easy to discover, understand, and store relevant information related to IoT devices. This work aims to present a Context-Aware System called CONASYS, a system able to sense the environment and to provide contextualized services to the users, meeting the users needs without specific knowledge of the environment, and improving the Quality of Experience (QoE). We present in details the architecture of CONASYS, the technical issues related to the implementation of the system, and evaluation tests.