Different simulation tools are available to the research community which can be used to validate, test and evaluate networking protocols. Such simulation software packages include OPNET, ns-2 and others. These programs are capable of performing relatively accurate simulations of networking architectures including wireless, ad hoc, and sensor networks. Although they are very useful for a wide range of experiments which involve performance evaluation of existing protocols, selecting them to verify and test the performance of new platforms and protocols that are not implemented in these programs tend to impose considerable restrictions and limitations. Therefore, implementing these protocols in existing simulator packages could be relatively difficult and time consuming. This paper presents an object-oriented framework to design an event-driven network simulator that can be used to evaluate different wireless networking architectures and protocols. The design of the simulator allows for a considerable increase in flexibility for the researcher who is able to include particular aspects and implementations of the corresponding protocols. The different classes that constitute the simulator application along with the main methods, and relationships are presented. In addition, design strategies for simulating node mobility using the popular Waypoint model are also presented.