There exists a variety of different peer-to-peer (P2P) protocols to support a wide range of distributed services, such as content distribution or data storage. In order to promote interoperability and facilitate the development of new P2P applications, common application programming interfaces (APIs) have been proposed. Unfortunately, most of these interfaces have stagnated, and fail to meet present research or business requirements. In this regard, this paper presents a novel common architecture and API which combines structured and unstructured overlay networks and strives to overcome the limitations of previous architectures. Our work defines a set of generalized components that are common in today's P2P systems, and provides a clean interface that facilitates the rapid development of new P2P applications and services. We validate the proposed architecture by presenting a concrete implementation including a broad range of protocols within the P2P simulator OverSim.