Research And Implementation Of Local Area Network Instant Communication System Based On Android Platform

Since the mobile Internet era,mobile instant messaging software,represented by WeChat and QQ,has developed rapidly and gained widespread application.With the feature of speediness and convenience,mobile instant messaging software is becoming an indispensable tool in people's work and life.But mobile instant messaging software which is currently on the market need connect to servers on the Internet to communicate with others.In the case of text communication only,this approach is not a problem.However,in real-time voice communications,especially in cluster voice communications,because the amount of voice data is large,then the consumption of traffic will produce no small overhead.On the other hand,Wi-Fi network is becoming more and more popular,building a simple wireless LAN requires only one wireless router.Therefore,in some scenarios,there is a need for a instant messaging system for mobile terminals,so that users can quickly and easily do person-person or group instant messaging through the wireless LAN,even if they do not connect to the Internet.In the instant messaging system,text communication and real-time voice communication are the most basic and the most important two requirements.Aiming at these two main requirements,this paper presents a design scheme of mobile terminal instant communication system under wireless local area network,and realized the scheme.For the text communication function,this paper chooses the XMPP protocol as the text communication protocol.After a detailed analysis of the XMPP protocol and the background architecture of Openfire,the scheme of using the Openfire server and the Smack library to construct the text communication system is given.And around the registration and login,contact management,chat session these three aspects gives a method to construct the client.For the voice communication function,this paper analyzes the structure of the voice communication system,and gives the architecture design of the voice communication system.The system uses the HTTP-based session control protocol designed in this paper.The client and server use modular design,including audio capture and playback module,voice compression codec module,data transceiver module and audio mixing module.Aiming at several key problems of voice communication system,this paper gives the solution.On the synchronization strategy of voice,a synchronization scheme driven by user data is given,which solves the problem of time alignment of voice data before mixing.On the problem of voice mixing algorithm,several different mixing algorithms are discussed,and the mixing algorithm suitable for different scenarios is analyzed.On the issue of voice jitter,a buffer-based scheme is given,so that the voice is smoother.For the problem of echo cancellation,the theory of echo cancellation is introduced and the solution based on Android's built-in API is given,which can effectively alleviate the echo problem when users use speakers.In addition,aiming at the dynamic access problem of the user,an optimization scheme is given.By caching the objects with large creation overheads,the access cost of dynamic access is reduced and the efficiency of the server is improved.Finally,this paper gives a concrete test scheme for this instant communication system,and verifies the usability of each function of the system.