Research And Realization Of IP Softphone Based On The Open Source SIP Protocol Stack

Early at February of 1995,the Internet Phone,the first long-distance telephone software,appeared in the world.From then on,VoIP is developed most rapidly in the field.It is improved from voice communication to multimedia communication,which is gradually combined with the fixed communication,the mobile communication and the Internet business.The definite aim of VoIP heads to Next Generation Network During the development process to Next Generation Network,how to choose the signaling protocol is the focus of contention,which is the key protocol of VoIP.The SIP is accepted gradually by people due to its more simplicity,flexibility and convenience among the protocols.Therefore,it becomes one of the key protocols of Next Generation Network.Thus,the SIP and its related technology are worth researching in application at present, and will be the key technology of Next Generation Network system in the future. Consequently the SIP and its open source project "ReSIProcate" are choosen to be the research subject,as well as further researched and discussed.A SIP telephone terminal software is realized to test the project, and related techniques are discussed and realized in the paper.Firstly,The VoIP technology and the SIP are briefly introduced in this article,and compared with existing open source SIP protocol stacks.Then, the stable and compatible multi-operating system's ReSIProcate project is chosen.The analysis of ReSIProcate's structure and design framework, along with the stack's concept packaging and implementation about elements of SIP,are deeply discussed in this paper.On the one hand,it lays the foundation for the research,on the other hand,it can be used in reference and records for open source project ReSIProcate,which is mature,stable but with limited documents.Then,the terminal software of SIP phone is systematically analyzed and designed in this paper,and the development process is fully brought up.The software is based on Visual Studio 2005 development tool and running on the Windows XP operating system.In the design of software,multithread mechanism can guarantee the modules parallelly running,the user-friendly interface is designed by MFC class library,the stack project,which belongs to the ReSIProcate open source stack,is used as the SIP core module.The DUM project of ReSIProcate is also used as the call controlling core module.