Book excerpt: "Java P2P Unleashed" provides a single source for Java developers who want to develop P2P systems. The book explains the benefits of each technology and shows how to fit the P2P "pieces" together - both in building new systems and integrating with existing ones. starts with a discussion of the P2P architecture, referencing similarities with existing, familiar systems while previewing several types of P2P applications. It explains how to plan ahead for security, routing, performance and other issues when developing a P2P application. Each technology included in the book - JXTA, Jini, JavaSpaces, J2EE, Web services - is approached from a P2P perspective, focusing on implementation concerns Java developers will face while using them. The last section includes several large-scale examples of different P2P applications - managing content, building communities, integrating services, routing messages, and using intelligent agents to gather information. The final chapter looks ahead to future developments in Java P2P technologies.