What Are P2P Software Applications?
A good definition of P2P software was proposed by Dave Winer of UserLand Software many years ago, when P2P was first becoming mainstream. He suggests that P2P software applications include these seven key characteristics:
The user interface runs outside of a Web browser
Computers in the system can act as both clients and servers
The software is easy to use and well-integrated
The application includes tools to support users wanting to create content or add functionality
The application makes connections with other users
The application does something new or exciting
The software supports "cross-network" protocols like SOAP or XML-RPC
In this modern view of peer-to-peer computing, P2P networks stretch across the entire internet, not just a home local area network (LAN). Easy-to-use P2P software applications allow both geeks and non-technical people to participate.
Kazaa, Napster and More P2P Software Applications
The original MP3 file sharing system, Napster became the world's most popular internet software application almost overnight. Napster typified the new "modern" P2P system defined above: a simple user interface running outside of the browser supporting both file serving and downloads. Furthermore, Napster offered chat rooms to connect its millions of users and performed a new and exciting (in the sense of "controversial") service.
The name Napster referred both to the P2P network and the file sharing client that it supported. Besides being limited, in the beginning, to a single client application, Napster employed a proprietary network protocol, but these technical details did not materially affect its popularity.
When the original unregulated Napster service was shut down, several P2P systems competed for that audience. Most Napster users migrated to the Kazaa and Kazaa Lite software applications and the FastTrack network. FastTrack grew to become even larger than the original Napster network.
Kazaa has suffered from its own legal troubles, but various other systems, like eDonkey / Overnet, have continued the legacy of free P2P file-sharing software.
Popular P2P Applications and Networks
No one P2P application or network enjoys exclusive popularity today. Popular P2P networks include:
eDonkey
BitTorrent
Gnutella
and popular P2P applications include
eMule
BitTorrent
Limewire
Many businesses have been inspired by the success of P2P applications and are busily brainstorming potentially interesting new P2P software. However, some in the networking community believe that the success of Napster, Kazaa, and other P2P applications have little to do with technology and more to do with piracy. It remains to be proven whether mass-market P2P systems can translate into profitable business ventures.