Network enabled applications fulfill an increasingly important role in our society today. With more and more devices being connected to the Internet, it is important to understand how to build applications that can communicate with other applications.

We briefly identified and explained several of the technologies that Java uses to connect to a network. We illustrated how the InetAddress class can represent an IP address, and we used this class for several examples. The basic elements of the client/server architecture were demonstrated using UDP, TCP, and SSL technologies. They provide different types of support. UDP is fast but not as reliable or as capable as TCP. TCP is a reliable and convenient way of communicating, but is not secure unless used with SSL.

The NIO support for buffers and channels was illustrated. These techniques can result in more efficient communications. The scalability of an application is critical for many applications, specifically the client/server model. We also saw how threads can support scalability.

Each of these topics will be addressed in more detail in later chapters. This includes the support NIO provides for scalability, how P2P applications work, and the myriad of interoperability technologies that are available for use with Java.

We'll start with a detailed examination of networks, and network addressing, in particular, in the next chapter.