Instant Messaging System Design And Implementation,

Instant Messaging (IM) is the highlight of current Internet applications, which provides web users with real-time, effective communications by organizing virtual Internet community. With the evolvement of IM to integrated web portal, and the advancement of IM to enterprise applications, studies on IM systems become more and more important. However, little result has been documented yet.In practice of our Directed IM Project, we encountered some fundmental problems: i. WHAT can IM provide for users?ii. HOW to design an IM protocol?iii. HOW to implement an IM system, especially an IM server? When resolving these problems, some other questions raise: i. HOW can IM system be employed in other form?ii. HOW to design application protocols? iii. HOW to construct general network server frameworks?The formal questions are engineering whereas the latter are more theoretical. Focusing on these topics, we present our solutions and thinking in this paper. Application protocol designing and application framework constructing solutions are innovated. Together with these two, issues that cover almost all facets of IM systems, including conceptual model, protocol designing, server algorithms analysis and implementation, are addressed in detail in this paper.Following contents can be found in this paper:First, the mapping between IM abstract model and IM systems in practice is described. Secondly, by using some application protocol designing laws extracted from TCP/IP protocol family, the round-trip IM protocol designing is demonstrated. After subtle comparisons of algorithms for network server constructing, a schema for an effective IM server is brought out. By introducing Design Pattern, the most newly developed Objected-Oriented technique, an application framework with remarkable flexibility and extensibility is concluded from the Directed IM Project programming. At last, the tendency of IM systems and problems to be conquered are listed out.