The vision of pervasive or ubiquitous computing, conceived by Mark Weiser, foresees a world where computing is embedded in every day objects. Such objects interact with each other to perform actions on behalf of the user. As one of the mains of pervasive computing is to disappear from human perception, applications embedded in electronic devices must be proactive. This indicates that they should guess the needs of the users in order to provide them with anytime, anywhere relevant information. This characteristic must be achieved by acquiring information not only about the user, but also about the environment where he/she is immersed. This kind of information can be obtained by interacting with nearby hosts, trough a variety of networking protocols. Applications can take advantage of this characteristic by performing host discovery through heterogeneous networks, possibly at the same time. However, due to memory and storage constraints, it is not reasonable to embed all of such protoco...