The World of Peer-to-Peer (P2P)/Networks and Protocols/IM

Instant Messaging
Instant messaging can be considered a subtype of P2P, in simple terms it consists on the act of instantly communicating between two or more people over a network (LAN or WAN) mostly using text. This requires the use of a client program so that when a message is sent, where a notification is shown a short time after on the destination application, enabling it's user to reply to the original messages. IM protocols can be centralized or distributed or a mix of the two.

Instant messaging allows users to send quick notes or reminders to other users in almost real time. IM can, but may not, include any P2P implementation or support extra P2P services like, file-sharing, VoIP or Video Conference the broad definition is that IM is the almost instantaneous trading of messages, whatever form it takes.

Since any P2P network depends on participation, supporting some kind of IM implementations is very important as a way to create a community and sustain the network.

IM Software Implementations

 * Gaim/Pidgin ( http://pidgin.im/pidgin/home/ ) OpenSource (GPL) instant messaging client supporting Windows, GNU, BSD, and many Unix derivatives and compatible with AIM, ICQ, MSN, Yahoo!, IRC, Jabber, Gadu-Gadu, SILC, GroupWise Messenger, and Zephyr networks.
 * Trillain ( http://www.ceruleanstudios.com/ ) skinnable chat client that supports AIM, ICQ, MSN, Yahoo!, and IRC, it also includes many features not included in those chat programs.
 * BitWise IM (http://www.bitwiseim.com), Encrypted Cross-Platform (Windows, Mac OS X, and Linux) Instant Messaging, free but closed source, uses wxWidgets. Also supports a Whiteboards, Voice Chat.
 * digsby (http://www.digsby.com), a closed source, windows only, multiprotocol IM client that lets you chat with all your friends on AIM, MSN, Yahoo, ICQ, Google Talk, and Jabber with one simple to manage buddy list.
 * Google Talk (http://www.google.com/talk/), Windows XP+ only, closed source, supports IM and interacts with the Gmail (google WEB mail) platform.