The Research And Implementation Of P2P Instant Messaging System Based On XMPP

As the rapid increment of Chinese Internet users, Instant Messaging (IM) plays a more and more important role in our lives. It becomes a major communication tool over networks. Instant Messaging is a collection of technologies used for real-time text-based communication between two or more participants over the Internet, or other types of networks. The major advantage of IM over other communication techniques is its synchrnoized information exchange approach which makes it real-time. Some systems permit messages to be sent to people not currently 'logged on', which is also called offline messages. This behavior removes some of the differences between IM and e-mail. Many IM systems are using C/S architecture now, under this architecture, the server is the key point. It may become the bottleneck of the whole system. In recent years, the P2P technology is applied in IM field frequently. This thesis proposes a server-assistant P2P architecture. It makes a good balance between system management and system efficiency.Extensible Messaging and Presence Protocol (XMPP) is a popular IM protocol. It is an XML based, open standard protocol. XMPP uses an open systems approach of development and application, by which anyone may implement an XMPP service and interoperate with other organizations' implementations. XMPP even defines how to communicate with other non-XMPP protocols clients.Meanwhile, Network Address Translation (NAT) has become a mainstream technology at the phase of the transition from IPv4 to IPv6. It can map many internal hosts to one public IP address or the opposite. This technology can solve the problem of IP address shortage. It is very important to study the NAT traversal in the instant messaging system.This paper introduces the XMPP protocol, implements a P2P IM system based on XMPP protocol. The system is event-driven, and uses observer model. The system's main features are: register, login, friend management and text chat. Then this paper analyzes the mechanism of NAT, presents the in-depth study of the NAT traversal in P2P communication, and decides to use STUN to resolve the problem of P2P communication.