| With the vigorous development of the Internet, instant messaging(IM) has been applied more and more widely in the application and it has gradually became an essential network service in daily life. But the current well-known instant communication systems have all adopted the proprietary IM protocols, leading to the fact that the instant messaging software cannot communicate with each other. Besides the current instant communication software mostly concentrate on the windows platform, seldom considering the needs of Linux users.This thesis presents the design of a cross-platform instant communication system scheme based on SIP protocol, which aims at using an opening and extension of the standard SIP protocol to solve the problem that the instant messaging software cannot interact with each other, caused by proprietary protocol. SIP protocol is a mature and strong compatibility application layer signaling control protocol,which can be used for audio/video session establishment, modification and release, and also it can realize the sending/receiving of instant message. Furthermore,SIP and its extended protocol have good expansibility, and thus it has become one of the most important protocols in the NGN and IMS networks. It is also one of the most important reasons that the SIP protocol is chosen as the basic protocol of instant messaging system.Qt is a cross-platform C++ application and UI development framework, and its development objective is: One Development, Deploy Anywhere. Namely, application developers only need one time to develop the application program and the program can be run in different operating systems. It realizes the real meaning of the cross-platform development. In this thesis, Qt is used as the development framework to achieve the goal that the same instant messaging application can interact message with others in different operating systems.Approaching from the SIP and its extended protocol, the main technical requirements of instant communication system is analyzed and the overall framework of the instant communication system is designed in this thesis. From the perspective of function modules,the instant messaging system can be divided into user management function module, contact list management functions module, IM instant message management function module, presence presents management functions module and group management module, and so on. The focus of this thesis are the contact list module, IM module and presence module, which are also the basic services of instant communication application. The contact list is responsible for the maintenance of the contact information and contacts added or deleted operation; IM module is responsible for instant message services, which includes the sending and receiving message between users;Presence service module mainly processes the presence service, including the publication, subscription and notification of the presence information.Finally, the system functional testing is carried out. The result shows that the instant communication application developed in this thesis is implemented the major instant communication functions, which including buddy-list management and the multimedia information interaction. It can be used as a reference for the design of products because of its stable system and simple interface. |
PDF Full Text Request