| As a vital component of multimedia applications, the multimedia conference contributes a lot for social information exchange. During the past decades, nowadays, there are two kinds of prevalent multimedia conference systems. One is based on H.323, and the other one is based on SIP. However, due to the simplicity and flexibility of SIP multimedia conference system, it is with more extensive use. In this background, various companies and associations have developed their own SIP user agent, such as X-Lite by Xten, sip-communicator, QuteCom and so on. These user agent products support standard SIP protocols, and can also hold network conferences. But most of them are desktop applications which cannot run in Web browser. Furthermore, most of the SIP user-agents are developed in C++ language, so even if they can be developed as ActiveX plug-in and embedded into IE browser, there are also two problems. Firstly, some kinds of browser support ActiveX not very well, except IE; secondly, they can only run in Windows platform. As B/S mode is with great popularity, the SIP agent which is able to run in Web browser and with great portability is a hot research direction.In this thesis, we design and implement an SIP user agent, which can run in web browser, based on Multimedia Conference System. It can be used to control conference and do media communication with other conference members. The SIP user agent is an Applet which is developed on the basis of JAIN SIP APIs and Java media framework (JMF), and can run in web browser. This feature is convenient to users because, without installing any software, it is just need to open the link can the SIP agent run. Futher more, by inheriting good portability of Java language, the SIP agent can run in kinds of operating systems and kinds of popular Web browsers as long as Java Virtual Machine is installed there. Sip user agent also adds the NAT traversal feature which confirms that the SIP user agent can run successfully under different network environment.The main content and contribution are listed below. First, a demand analysis of the SIP user agent is made, and a brief introduction to its location in the whole media conference system is introduced. Then, the whole software architecture is shown, and then each module is introduced separately in detail. Futher more, the problems, such as how to make the agent run without the JMF installation and how to apply the agent with NAT feature, are solved. In addition, several test cases are used to test the demo system. At last, we summarize our work and also take a further view of both the aim and the research area. |
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