Chapter 3. P2P Application Types

by Robert Flenner and Frank Cohen

In This Chapter

• Instant Messaging

• Managing and Sharing Information

• Collaboration

• Distributed Services

Chapter 1 introduced the wide world of P2P. It might have appeared that the definition of P2P is problematic well, it is! P2P can be so broad in scope and definition that getting one's arms around P2P can be an enormous task. P2P came about as an answer to user needs for Internet-enabled application software. The Internet is always evolving and offering up new technologies, techniques, and user behavior every day. P2P is evolving along with the Internet, so fixed definitions do not usually last long.

Each new advance in Internet technology can either help Java developers working on Internet applications, or become a huge headache. For example, there was a time when Network Address Translation (NAT) routers were banned from networks. As you will see later in this chapter, they are now used widely, and a Java developer building a P2P application needs a solution to the unique one-way routing provided by a NAT router.

An easy way to get your arms around a P2P definition is to look at the functions delivered by the most notable P2P applications, including the following:

• Instant messaging

• Managing and sharing information

• Collaboration

What started out as simple file sharing, such as exchanging music files, has grown to include a wide array of applications and services. These are grouped under the umbrella term distributed P2P services. These include network and infrastructure software to enable

• Distributed processing (grid computing)

• Distributed storage

• Distributed network services

Although many of these applications began as ways to distribute stolen copyrighted music and video files, P2P has reached a level of maturity that is no longer confined to personal, casual use, but rather to build e-market hubs, corporate infrastructure, and Internet-enabled applications. In addition, single-function P2P applications are giving way to multifunction service-based architectures. For instance, it is common to aggregate instant messaging, file sharing, and content management to build distributed collaborative P2P applications.

Next we will look in depth at these applications and the technology that enables them.