Despite their crucial impact on the performances of P2P systems, very few is known on peers behaviors in such networks. We propose here a study of these behaviors in a running environment using a semicentralised P2P system (eDonkey). To achieve this, we use a trace of the queries made to a large server managing up to fifty thousands peers simultaneously, and a few thousands queries per second. We analyse these data using complex network methods, and focus in particular on the degrees, their correlations, and their time-evolution. Results show a large variety of observed phenomena, including the variety of peers behaviors and heterogeneity of data queries, which should be taken into account when designing P2P systems.