m-torrent: Torrent System within Wireless Network for Java Supported Mobile Phones Nitesh Kumar Rohit V. Gugale Jatin J. Kakani Rahul G. Dalal Abstract: Since the advent of internet, data sharing has got its own importance. Today most of the organizations and college campuses have private wireless networks for internet access. However, apart from using them merely for accessing the internet, it will be great if we can use them for sharing the data within that network. Also in today s world many people have wifi enabled mobile phones with lots of storage capacity which are active 24x7. For most of the time, these devices are in idle state. But we can use them for other purposes. It will be great if we use our mobile phones to share files within a wireless network without any need of internet access. Our idea is to create a wireless peer-to-peer bit torrent-like file sharing system which will allow users to search and download interested data from other users while they are within the range of the wireless network. Colleges can deploy this system within their campus so that all the students in the campus can share their files while they are in campus. Also organization can use this system in their buildings so that all employees can share their data. Keywords- BitTorrent, mobile torrent, wifi enabled mobile phones, wireless LAN, wireless access point, J2ME I. INTRODUCTION When mobile phones first came into picture, analog signal was used and no data service was supported. After we entered the era of digital signal, GSM emerged but it only supports several simple data services, e.g. Short Message Service (SMS). Although the 2.5G technology General Packet Radio Switch (GPRS) greatly improves the data rate, it is still not enough. 3G is an excellent service for future wireless communication world. Providing an average data rate of 384Kb/s and help of other relevant protocols, 3G mobile phones can literally support any data services that have been implemented in the Internet. We know that data sharing has always got its own importance. Gradually data sharing over the internet came into picture. It enabled people to share their data or files with people whom they know. P2P proved to be very useful. With the advent of internet, file sharing gained a lot of importance. However, prior to the discovery of Bit Torrent, users used to share the data only with those whom they knew. Bit Torrent made it possible for unfamiliar users to share data with each other. In this paper, a system for sharing the data between two unfamiliar users in a wireless network is discussed. II. BACKGROUND Our work is greatly based on two technologies: Peer-to- Peer network and a prototype of BitTorrent Protocol. In this section, we explain the general background of these technologies. A. Peer-to-Peer network [2] P2P network architecture has changed the traditional network built on Client-Server model. When several computers are interconnected, but no computer occupies a privileged position, the network is usually referred to as a peer-to-peer network. In this type of network, every computer can communicate with all the other machines on the network, but in general each one stores its own files and runs its own applications. With a client-server network, one or more servers will perform critical functions on behalf of the other machines (the clients) on the network. These functions consist of user authentication, data storage, and the running of large, shared, resource-intensive applications. Typically, both peerto-peer and client-server networks rely on a shared Internet connection for access to external resources of these basic network structures. 167
There are three major types of P2P network architecture. The first type is centralized topology which needs a central server for peers and resource discovery. The second one is decentralized unstructured topology which is also called pure P2P. It does not involve any central server and every node has equal functionality. The last one is decentralized structured topology, which is also called hybrid P2P. It is a mixture the first and the second type, where there exist several super-peers for peer and resource discovery. B. A prototype of BitTorrent Protocol [3] Complete BitTorrent file distribution system consists of following entities [1] : A static metadata file (torrent file) consisting of the content to be shared A web server for publishing torrent files (or published by other means) A BitTorrent tracker An original peer publishing content which may move out of the network if the whole content is available among other peers in the system Web browser for finding torrent files A downloader application to handle torrent files and operate in the BitTorrent network. C. Full Text Search Mechanism In present days searching is a very common operation which performed on databases. While performing search by SQL queries based on select statements with where clause it is okay for small databases but a large database may cause slow result. A WHERE LIKE clause is not efficient in such cases. For example if you consider a search engine like Google it is a poor idea to use where like clause to perform search based on text. Two basic problems are: first, slow processing and second, less accurate result set. Both of the above disadvantages has been overcome by the introduction of full text search, which compare strings instead of character sequence and provide best accuracy. Also creation of full text index solves the problem of speed of operation. The clause MATCH()..AGAINST() of MySQL enables us to compare a sentence against multiple columns of a table at once. Full-text indexes can be used only with MyISAM tables, and can be created only for CHAR, VARCHAR, or TEXT columns. Full text search can be performed in any of three modes: Natural Language Mode Boolean Mode Query Expansion Mode 1. Working: The originating user (the seed) makes available one copy of the file, which is then split up into chunks. Different chunks are sent out to the various computers (BitTorrent clients) trying to get hold of a copy of the file. Figure 1: Download Protocol Each client uploads their part of the file to other clients while simultaneously downloading bits of the file they don't have from other clients. All the clients work together as a swarm to share the file. The file-sharing process doesn't happen in the systematic, sequential way. Clients upload and download simultaneously and the file actually builds up in a more random way. There are often hundreds of clients involved in each swarm. Eventually, every client receives a complete copy of the file. Thus the data can be shared to a large no. of users with a minimum overhead on original seeder. Following points lists the features of BitTorrent: Multisource downloading i.e. simultaneous downloading from multiple sources Simultaneously uploading and downloading the content A tit-for-tat policy provides very efficient spreading of the content Integrity checks which are done at the piece level One corrupted piece does not ruin the complete download process. III. MOTIVATION As of today, very less work has been done for file sharing using mobile over the wireless networks. We rarely use wireless network for purposes other than using internet. Hence wireless networks are not used to their full capacity. Also, we have mobile phones that are ON 24x7 having high storage capacities and capable enough to transfer files with similar other devices. So can we design a system to 168
provide a platform for sharing data under a private wireless network among people having wifi enabled mobile phones? IV. PROPOSED SYSTEM Our aim is to design a platform independent BitTorrent like system for wifi enabled mobile phones in a wireless local area network for data sharing Thus, the aim of this project is to develop a BitTorrent - like system for mobile phones where users can exchange data with other users whom they may or may not know but are connected to the same wireless LAN. The proposed system will provide an efficient way to use the wireless networks for file sharing. V. SCOPE The system is limited to a particular wireless LAN. Users connected within the same wireless LAN where system is deployed can download and share the data with other users. The peer-to-peer file sharing will be possible only till the users remain within the range of wireless network. This system is not developed for internet users. That is, the domain for our system is a wireless local area network. VI. SYSTEM ARCHITECTURE m-torrent system is divided into two components: Figure 2: Architecture of m-torrent System A. Server: Server will be deployed in college campus or in the organization. It is connected with wireless access point. Module running on server is developed in J2EE which consists of two parts: 1. Searching Module: which will allow users to search for a specific torrent. 2. Tracker Module: which will keep track of live traffic for each torrent, that is, it will maintain a list of mobile phones which are currently downloading the same torrent file. B. Client: Client module is mobile application developed in J2ME which is installed on mobile devices. This application will be used to- connect to the server for creating a torrent file for downloading data using the torrent file The system implements both client - server as well as adhoc network architecture. For functionalities like search, create, upload and download torrent file, each mobile phone directly communicates with the server. Thus, the system implements client-server architecture. On the other hand when mobile phones are exchanging data among them, they are connected in a mesh topology hence they are using ad-hoc network architecture. VII. IMPLEMENTATION A. Assumptions: It is assumed that the m-torrent application is installed on user s cell phone to facilitate the sharing of files. The users have wifi enabled mobile phones supporting java environment. The users are connected to the same wireless LAN. Server is connected with wireless network and server module is deployed on it. B. Implementation Constraints: Necessary requirement for this system is that at least one seeder should be available in the wireless network who has complete copy of the data. Also user downloading the file must remain in the range of wireless access point to continue download. User can t download file having size greater than available memory. C. Working: 1) Creating and uploading a torrent file: The client user who wants to download the file is going to use a metadata file to initiate download. This metadata file is called as mtorrent file which needs to be created first. The creation of m-torrent file is done by the initial seeder using the same client application. During the creation of mtorrent file, all file specifications are recorded in it. While creating a torrent file for specific file or for directory which contains the data, the user needs to- 1. Select the path of that file or directory in mobile phone 2. Name the torrent file 3. Select the chunk size in which the file will be divided Once user provides all the information, file is divided into no. of chunks. A hash code for each chunk is then calculated. 169
IRACST International Journal of Computer Networks and Wireless Communications (IJCNWC), ISSN: 2250-3501 Also, a key specific to that torrent file is calculated. A torrent file is created and all this information is stored into torrent file. search for all available torrent files. These results are then sent back to user using wireless network. c) After receiving results user will select particular result to download torrent file associated with it. This request is sent to server and in reply server sends copy of torrent file back to user. Figure 3: Creating and uploading a torrent file Client now connects to the server and sends request to upload a torrent file. Once server agrees, torrent file is uploaded on the server where server lists that file in its records and starts tracking that torrent. 2) Getting a torrent file To start downloading actual data file user is required to have a torrent file for the same. There are two ways to get it. Either user can directly get it from any of his friend by file copy or he can search the torrent system database and then can select and download any one of the listed search results. During search the mobile client application sends the query in string format to the server. Server uses full text search to dig the related files and result see is sent back to client in a bunch of 10 results every time the client requests for more results. The result is interpreted at client end. And after selection of any result for download the torrent file is downloaded to the mobile. Now the user can proceed for the data file download. The torrent file, being very small in size, is downloaded very fast. The maximum size of torrent file is found to be less than 1KB in our case during testing. 3) Downloading a file: As shown in fig.4, user will first install m-torrent client application on his/her mobile. a) Using m-torrent client application user will connect to server and if he/her wants to download any data, he/she will enter search query in application. b) This request will be sent to the server where Search module running on server will process this query and will Figure 4: Downloading of data This torrent file contains: i) File/Directory name ii) Date of creation iii) Total size of data iv) Tracker address v) No. of pieces vi) A key for uniquely identifying a torrent file vii) A hash code for each piece Now as the user has torrent file, he can now start downloading the actual data. d) To start downloading user first selects corresponding torrent file and clicks on start download option. As user clicks on start download option query is sent to server to get list of seeders and leechers i.e. other mobiles which are downloading the same file or having a copy of it. e) When this request is received by server, tracker module running on server will send list of seeders and leechers back to user. f) After receiving this list, m-torrent creates separate connection with each peer and can now start downloading the file. 170
VIII. FUTURE SCOPE m-torrent system can be further integrated with current bittorrent system over the internet. For such integration, work of the server will be done by existing bit-torrent system and our mobile application will act as client for the user for downloading data. Our current system can be further extended to support free Video calling, SMS and Chat service within wireless network. All the users which are connected to the system can talk to each other using video calling. For this feature voice and video will be sent in the form of packets to both devices and at the user side conversion will be done back to original form. For such calling, function of authentication and call management will be done by server. Also using the same technique, user can send SMS to any other user who is within the range of wireless network and is using our application. Chatting service is also possible to implement with current system. m-torrent client application can have chat option where user will first select other user for chat. This request for chat will be sent to other user. When that user confirms request chat service can be initiated where conversation will be sent in the form of packets to both parties. IX. CONCLUSION In this paper we have presented a system whose aim is to provide a platform for data sharing services in wireless network to mobile phones in a modular and adaptive way. The system will enable remote users within a wireless local area network to share data between them. Using this system, a wireless network can be used efficiently for data sharing along with internet usage. Also the system utilizes the idle time of mobile phones to provide a powerful functionality without affecting other functionalities of mobiles. REFERENCES [1] Jani Peltotalo, Department of Communications Engineering, Tampere University of Technology, P2P File Sharing: BitTorrent in Detail [2] Liang Li, Xinshe Wang, P2P File-Sharing Application on Mobile Phones Based on SIP, 978-1-4244-1841-1, 2008 IEEE [3] Amir Krifa, Mohamed Karim Sbai, Chadi Barakat, Thierry Turletti, BitHoc: A content sharing application for Wireless Ad-hoc Networks [4] Baptiste Dubuis, Java bittorrent API, Lausanne, February 19, 2007 [5] Leonardi, G. Morabito, S. Palazzo, A. Panto, F. Scoto, ShareAnywhere: a platform for developing mobile sharing applications,2008 IEEE [6] http://dev.mysql.com/doc/refman/5.0/en/fulltext-search.html 171