CORDIAL is a collaborative service discovery strategy designed for mobile and opportunistic networks, which takes advantage of some features of human behavior, namely the periodicity of movements, the membership to a restricted number of communities and the sharing of interests among members of a community. CORDIAL exploits these features by adapting the strategies of query and service advertisements by exploiting the cooperation of nodes with higher social centrality in order to improve the chance of finding the desired service. The evaluation of CORDIAL by simulation shows that, as compared with similar approaches, it improves proactivity and accuracy levels, and it reaches performance comparable to the flooding technique but at a much lower cost.