Projet_JAVA_P2P_STRI2A/src/client/ClientManagementUDP.java

package client;
import exception.NotFound;
import exception.ProtocolError;
import exception.InternalError;
import exception.TransmissionError;
import java.utils.Scanner;
import java.net.InetAddress;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.io.File;
import java.io.IOException;

/** Implementation of P2P-JAVA-PROJECT VERSION 1.0 protocol for UDP.
 * @author	Louis Royer
 * @author	Flavien Haas
 * @author	JS Auge
 * @version	1.0
 */
public class ClientManagmentUDP implements Runnable {
	private String baseDirectory;
	private int UDPPort;
	private String host;
	private final String protocolID = "P2P-JAVA-PROJECT VERSION 1.0";


	/** Constructor for UDP implementation, with baseDirectory and UDPPort parameters.
	 * @param baseDirectory	the root directory where files are stored
	 * @param UDPPort	the server will listen on this port
	 */
	public ClientManagmentUDP(String baseDirectory, String host, int UDPPort) {
		this.baseDirectory = baseDirectory;
		this.host = host;
		this.UDPPort = UDPPort;
	}

	/** Implementation of Runnable
	 */
	public void run() {
		System.out.println("Files present on the server:");
		try {
			String msg = sendMsg(sendFileList());
			System.out.println(listDirectory(msg));
			System.out.println("Name of the file to download:");
			Scanner scanner = new Scanner(System.in);
			f = scanner.nextLine();
			msg = sendMsg(sendDownloadRequest(f));
			download(msg, f);
		} catch (ProtocolError e) {
			System.out.println("Protocol error");
		} catch (NotFound e) {
			System.out.println("File not found");
		} catch (InternalError e) {
			System.out.println("Server internal error");
		} catch (IOException e) {
			System.out.println("Cannot write to file");
		}
	}

	/** Prepare request to download file
	 * @param filename	name of the file to be downloaded
	 * @return	request to be send
	 */
	private String sendDownloadRequest(String filename) {
		return protocolID + "\nDOWNLOAD\n" + filename + "\n";
	}

	/** Download file.
	 * @param response	Servers's response
	 * @throws NotFound
	 * @throws ProtocolError
	 * @throws InternalError
	 */
	private void download(String response, String filename) throws NotFound, ProtocolError, InternalError, IOException {
		try {
			String r[] = r.split('\n', 3);
			checkProtocolID(r[0]);
			String r2[] = r[1].split(' ');
			if (r2[0] != "LOAD") {
				throw ProtocolError;
			}
			int size = Integer.parseInt(r2[1]);
			if (r[2].length() != size) {
				throws TransmissionError;
			}
			FileWriter fileWriter = new FileWriter(baseDirectory + f);
			fileWriter.write(r[2]);
			fileWriter.close();
			 
		} catch (java.lang.ArrayIndexOutOfBoundsException e) {
			throw ProtocolError;
		} catch (ParseException e) {
			throw ProtocolError;
		}
	}

	/** Prepare request to list files on server
	 * @return	request to be send
	 */
	private String sendListDirectoryRequest() {
		return protocolID + "\nLIST\n";
	}

	/** Parse list of directory response from server
	 * @param response	server's response
	 * @return	list of files, separated by CRLF
	 * @throws ProtocolError
	 */
	private String listDirectory(String response) throws ProtocolError {
		try {
			String r[] = r.split('\n');
			checkProtocolID(r[0]);
			return r.split(protocolID + "\nLOAD \n")[1];
		} catch (java.lang.ArrayIndexOutOfBoundsException e) {
			throw ProtocolError;
		}
	}
	
	/** Check client's protocol identifier matches message's protocol identifier.
	 * Throws a ProtocolError if mismatched.
	 * @param msgProtocolID	part of the request containing protocol identifier
	 * @throws	ProtocolError
	 */
	private void checkProtocolID(String msgProtocolID) throws ProtocolError {
		if (protocolID != msgProtocolID) {
			throw ProtocolError;
		}
	}

	/** Send message to server
	 * @param msg	message to be send
	 * @return	server's response
	 */
	private String sendMsg(String msg) {
		InetAddress dst = InetAddress.getByName(host);
		byte [] bytesString = msg.getBytes();
		DatagramPacket emission = new DatagramPacket(bytesString, bytesString.length, dst, UDPPort);
		socket.send(emission);
		socket.receive(reception);
		return new String(reception.getData(), 0, reception.getLength());
}