In this paper we present a Colored Petri Net (CPN) for a multi-agent application. In particular we modeledthe Packet-World. In our research we use the packet-world as a case to study the fundamentals of agents'social behavior. Our approach is to combine experiments with conceptual modeling. We start from a verybasic model and then add social skills in a modular way. Integrating new social skills by means of addingnew modules offers us a clear conceptual view on the evolution of agents and the environment. With aconceptual view we mean: (i) which concepts does an agent need in order to acquire a new kind of socialability, (ii) which infrastructure is necessary in the environment to support these abilities, (iii) how do theseconcepts relate to each other? With the insights we learn from the case study, we gradually develop ageneric conceptual model for social agents situated in a MAS. In this paper we first present a CPN for abasic model of the packet-world. This model consists of agents that can only interact through passiveobjects in the environment. Because interaction is the central issue of multi-agent systems, we haveincorporated basic infrastructure for agent coordination straight away into our basic model. Then weextend the model, making it possible for the agents to communicate information with each other.Communication is the basis for social organization. Besides the concrete realization of a CPN for a multiagentapplication, the model we present in this paper has the potential to support our future research ofagents' social behavior. Our major motives for using CPNs as modeling tool are (i) CPNs gives a clearconceptual view on agents and the environment wherein they live, and (ii) CPNs support neat verificationand formalization.