PEER TO PEER

PEER TO PEER

• Peer-to-peer (P2P) is a decentralized communications model in which each party has the same capabilities and either party can initiate a communication session.
• Unlike the client/server model, in which the client makes a service request and the server fulfills the request, the P2P network model allows each node to function as both a client and server.
• P2P systems can be used to provide anonymized routing of network traffic, massive parallel computing environments, distributed storage and other functions. 
• Most P2P programs are focused on media sharing and P2P is therefore often associated with software piracy  and copyright violation.
• In its simplest form, a peer-to-peer (P2P) network is created when two or more PCs are connected and share resources without going through a separate server computer.
• A P2P network can be an ad hoc connection—a couple of computers connected via a Universal Serial Bus to transfer files.
• A P2P network also can be a permanent infrastructure that links a half-dozen computers in a small office over copper wires.
• Or a P2P network can be a network on a much grander scale in which special protocols and applications set up direct relationships among users over the Internet. .

P2P ENVIRONMENT

·         In a P2P environment, access rights are governed by setting sharing permissions on individual machines. 

EXAMPLE:  

• if User A's PC is connected to a printer that User B wants to access, User A must set his machine to allow (share) access to the printer. 
• Similarly, if User B wants to have access to a folder or file, or even a complete hard drive, on User A's PC, User A must enable file sharing on his PC. 
• Access to folders and printers on an office P2P network can be further controlled by assigning passwords to those resources

Navigating a P2P Network

            This diagram shows how a P2P network operates. The solid lines indicate physical, hard-wired network cables. The dotted lines indicate that each PC can communicate and share files with every other PC on such a network. A printer attached to one PC can be used by other PCs on the network—if that printer’s PC allows such use.

CLASSIFICATION: P2P can be classified in several ways. We will use a couple of common classification categories that are useful in understanding the nature of P2P networks. One classification is based on how indexing, the process of finding a node, is performed:

• Centralized: This is when a central server keeps track of where the data is located among peers
• Local: This is when each peer keeps track of its own data
• Distributed: This is when the data references are maintained by multiple peers

Hybrid P2P networks use a centralized indexing scheme. Pure P2P networks use local or distributed indexes.

P2P FILE SHARING: SENDER

import java.net.*;

import java.io.*;

public class Server {

             public static void main (String [] args ) throws IOException {

                         

                            ServerSocket serverSocket = new ServerSocket(15123);

                              Socket socket = serverSocket.accept();

                              System.out.println("Accepted connection : " + socket);

                              File transferFile = new File ("D:\\P2PFILE\\SENDER.txt");

                              byte [] bytearray  = new byte [(int)transferFile.length()];

                              FileInputStream fin = new FileInputStream(transferFile);

                              BufferedInputStream bin = new BufferedInputStream(fin);

                              bin.read(bytearray,0,bytearray.length);

                              OutputStream os = socket.getOutputStream();

                              System.out.println("Sending Files to Client...");

                              os.write(bytearray,0,bytearray.length);

                              os.flush();

                              socket.close();

                              System.out.println("File transfer complete");

                            }

}

P2P: CLIENT

import java.net.*;

import java.io.*;

public class Client {

            public static void main (String [] args ) throws IOException {

                int filesize=1022386;

                int bytesRead;

                int currentTot = 0;

                Socket socket = new Socket("127.0.0.1",15123);

                byte [] bytearray  = new byte [filesize];

                InputStream is = socket.getInputStream();

                FileOutputStream fos = new FileOutputStream("D:\\P2PFILE2\\RECEIVED.txt");

                BufferedOutputStream bos = new BufferedOutputStream(fos);

                bytesRead = is.read(bytearray,0,bytearray.length);

                currentTot = bytesRead;

                do {

                   bytesRead =

                      is.read(bytearray, currentTot, (bytearray.length-currentTot));

                   if(bytesRead >= 0) currentTot += bytesRead;

                } while(bytesRead > -1);

                bos.write(bytearray, 0 , currentTot);

                bos.flush();

                bos.close();

                socket.close();

              }

}.