+package bittorrent;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map.Entry;
+
+import org.simgrid.msg.Comm;
+import org.simgrid.msg.Host;
+import org.simgrid.msg.Msg;
+import org.simgrid.msg.MsgException;
+import org.simgrid.msg.Process;
+import org.simgrid.msg.Task;
+
+/**
+ * Main class for peers execution
+ */
+public class Peer extends Process {
+ protected int round = 0;
+
+ protected double deadline;
+
+ protected int id;
+ protected String mailbox;
+ protected String mailboxTracker;
+ protected String hostname;
+ protected int pieces = 0;
+ protected char[] bitfield = new char[Common.FILE_PIECES];
+ protected short[] piecesCount = new short[Common.FILE_PIECES];
+
+ protected int piecesRequested = 0;
+
+ protected ArrayList<Integer> currentPieces = new ArrayList<Integer>();
+ protected int currentPiece = -1;
+
+ protected HashMap<Integer, Connection> activePeers = new HashMap<Integer, Connection>();
+ protected HashMap<Integer, Connection> peers = new HashMap<Integer, Connection>();
+
+ protected Comm commReceived = null;
+
+ public Peer(Host host, String name, String[]args) {
+ super(host,name,args);
+ }
+
+ @Override
+ public void main(String[] args) throws MsgException {
+ //Check arguments
+ if (args.length != 3 && args.length != 2) {
+ Msg.info("Wrong number of arguments");
+ }
+ if (args.length == 3) {
+ init(Integer.valueOf(args[0]),true);
+ }
+ else {
+ init(Integer.valueOf(args[0]),false);
+ }
+ //Retrieve the deadline
+ deadline = Double.valueOf(args[1]);
+ if (deadline < 0) {
+ Msg.info("Wrong deadline supplied");
+ return;
+ }
+ Msg.info("Hi, I'm joining the network with id " + id);
+ //Getting peer data from the tracker
+ if (getPeersData()) {
+ Msg.debug("Got " + peers.size() + " peers from the tracker");
+ Msg.debug("Here is my current status: " + getStatus());
+ if (hasFinished()) {
+ pieces = Common.FILE_PIECES;
+ sendHandshakeAll();
+ seedLoop();
+ }
+ else {
+ leechLoop();
+ seedLoop();
+ }
+ }
+ else {
+ Msg.info("Couldn't contact the tracker.");
+ }
+ Msg.info("Here is my current status: " + getStatus());
+ }
+ /**
+ * Peer main loop when it is leeching.
+ */
+ private void leechLoop() {
+ double nextChokedUpdate = Msg.getClock() + Common.UPDATE_CHOKED_INTERVAL;
+ Msg.debug("Start downloading.");
+ /**
+ * Send a "handshake" message to all the peers it got
+ * (it couldn't have gotten more than 50 peers anyway)
+ */
+ sendHandshakeAll();
+ //Wait for at least one "bitfield" message.
+ waitForPieces();
+ Msg.debug("Starting main leech loop");
+ while (Msg.getClock() < deadline && pieces < Common.FILE_PIECES) {
+ if (commReceived == null) {
+ commReceived = Task.irecv(mailbox);
+ }
+ try {
+ if (commReceived.test()) {
+ handleMessage(commReceived.getTask());
+ commReceived = null;
+ }
+ else {
+ //If the user has a pending interesting
+ if (currentPiece != -1) {
+ sendInterestedToPeers();
+ }
+ else {
+ if (currentPieces.size() < Common.MAX_PIECES) {
+ updateCurrentPiece();
+ }
+ }
+ //We don't execute the choke algorithm if we don't already have a piece
+ if (Msg.getClock() >= nextChokedUpdate && pieces > 0) {
+ updateChokedPeers();
+ nextChokedUpdate += Common.UPDATE_CHOKED_INTERVAL;
+ }
+ else {
+ waitFor(1);
+ }
+ }
+ }
+ catch (MsgException e) {
+ commReceived = null;
+ }
+ }
+ }
+
+ /**
+ * Peer main loop when it is seeding
+ */
+ private void seedLoop() {
+ double nextChokedUpdate = Msg.getClock() + Common.UPDATE_CHOKED_INTERVAL;
+ Msg.debug("Start seeding.");
+ //start the main seed loop
+ while (Msg.getClock() < deadline) {
+ if (commReceived == null) {
+ commReceived = Task.irecv(mailbox);
+ }
+ try {
+ if (commReceived.test()) {
+ handleMessage(commReceived.getTask());
+ commReceived = null;
+ }
+ else {
+ if (Msg.getClock() >= nextChokedUpdate) {
+ updateChokedPeers();
+ //TODO: Change the choked peer algorithm when seeding
+ nextChokedUpdate += Common.UPDATE_CHOKED_INTERVAL;
+ }
+ else {
+ waitFor(1);
+ }
+ }
+ }
+ catch (MsgException e) {
+ commReceived = null;
+ }
+
+ }
+ }
+
+ /**
+ * Initialize the various peer data
+ * @param id id of the peer to take in the network
+ * @param seed indicates if the peer is a seed
+ */
+ private void init(int id, boolean seed) {
+ this.id = id;
+ this.mailbox = Integer.toString(id);
+ this.mailboxTracker = "tracker_" + Integer.toString(id);
+ if (seed) {
+ for (int i = 0; i < bitfield.length; i++) {
+ bitfield[i] = '1';
+ }
+ }
+ else {
+ for (int i = 0; i < bitfield.length; i++) {
+ bitfield[i] = '0';
+ }
+ }
+ this.hostname = host.getName();
+ }
+ /**
+ * Retrieves the peer list from the tracker
+ */
+ private boolean getPeersData() {
+
+ boolean success = false, sendSuccess = false;
+ double timeout = Msg.getClock() + Common.GET_PEERS_TIMEOUT;
+ //Build the task to send to the tracker
+ TrackerTask taskSend = new TrackerTask(hostname, mailboxTracker, id);
+
+ while (!sendSuccess && Msg.getClock() < timeout) {
+ try {
+ Msg.debug("Sending a peer request to the tracker.");
+ taskSend.send(Common.TRACKER_MAILBOX,Common.GET_PEERS_TIMEOUT);
+ sendSuccess = true;
+ }
+ catch (MsgException e) {
+
+ }
+ }
+ while (!success && Msg.getClock() < timeout) {
+ commReceived = Task.irecv(this.mailboxTracker);
+ try {
+ commReceived.waitCompletion(Common.GET_PEERS_TIMEOUT);
+ if (commReceived.getTask() instanceof TrackerTask) {
+ TrackerTask task = (TrackerTask)commReceived.getTask();
+ for (Integer peerId: task.peers) {
+ if (peerId != this.id) {
+ peers.put(peerId, new Connection(peerId));
+ }
+ }
+ success = true;
+ }
+ }
+ catch (MsgException e) {
+
+ }
+ commReceived = null;
+ }
+ commReceived = null;
+ return success;
+ }
+ /**
+ * Handle a received message sent by another peer
+ * @param task task received.
+ */
+ void handleMessage(Task task) {
+ MessageTask message = (MessageTask)task;
+ Connection remotePeer = peers.get(message.peerId);
+ switch (message.type) {
+ case HANDSHAKE:
+ Msg.debug("Received a HANDSHAKE message from " + message.mailbox);
+ //Check if the peer is in our connection list
+ if (remotePeer == null) {
+ peers.put(message.peerId, new Connection(message.peerId));
+ sendHandshake(message.mailbox);
+ }
+ //Send our bitfield to the pair
+ sendBitfield(message.mailbox);
+ break;
+ case BITFIELD:
+ Msg.debug("Received a BITFIELD message from " + message.peerId + " (" + message.issuerHostname + ")");
+ //update the pieces list
+ updatePiecesCountFromBitfield(message.bitfield);
+ //Update the current piece
+ if (currentPiece == -1 && pieces < Common.FILE_PIECES && currentPieces.size() < Common.MAX_PIECES) {
+ updateCurrentPiece();
+ }
+ remotePeer.bitfield = message.bitfield.clone();
+ break;
+ case INTERESTED:
+ Msg.debug("Received an INTERESTED message from " + message.peerId + " (" + message.issuerHostname + ")");
+ assert remotePeer != null;
+ remotePeer.interested = true;
+ break;
+ case NOTINTERESTED:
+ Msg.debug("Received a NOTINTERESTED message from " + message.peerId + " (" + message.issuerHostname + ")");
+ assert remotePeer != null;
+ remotePeer.interested = false;
+ break;
+ case UNCHOKE:
+ Msg.debug("Received an UNCHOKE message from " + message.peerId + "(" + message.issuerHostname + ")");
+ assert remotePeer != null;
+ remotePeer.chokedDownload = false;
+ activePeers.put(remotePeer.id,remotePeer);
+ sendRequestsToPeer(remotePeer);
+ break;
+ case CHOKE:
+ Msg.debug("Received a CHOKE message from " + message.peerId + " (" + message.issuerHostname + ")");
+ assert remotePeer != null;
+ remotePeer.chokedDownload = true;
+ activePeers.remove(remotePeer.id);
+ break;
+ case HAVE:
+ if (remotePeer.bitfield == null) {
+ return;
+ }
+ Msg.debug("Received a HAVE message from " + message.peerId + " (" + message.issuerHostname + ")");
+ assert message.index >= 0 && message.index < Common.FILE_PIECES;
+ assert remotePeer.bitfield != null;
+ remotePeer.bitfield[message.index] = '1';
+ piecesCount[message.index]++;
+ //Send interested message to the peer if he has what we want
+ if (!remotePeer.amInterested && currentPieces.contains(message.index) ) {
+ remotePeer.amInterested = true;
+ sendInterested(remotePeer.mailbox);
+ }
+
+ if (currentPieces.contains(message.index)) {
+ sendRequest(message.mailbox,message.index);
+ }
+ break;
+ case REQUEST:
+ assert message.index >= 0 && message.index < Common.FILE_PIECES;
+ if (!remotePeer.chokedUpload) {
+ Msg.debug("Received a REQUEST from " + message.peerId + "(" + message.issuerHostname + ") for " + message.peerId);
+ if (bitfield[message.index] == '1') {
+ sendPiece(message.mailbox,message.index,false);
+ }
+ else {
+ Msg.debug("Received a REQUEST from " + message.peerId + " (" + message.issuerHostname + ") but he is choked" );
+ }
+ }
+ break;
+ case PIECE:
+ if (message.stalled) {
+ Msg.debug("The received piece " + message.index + " from " + message.peerId + " (" + message.issuerHostname + ")");
+ }
+ else {
+ Msg.debug("Received piece " + message.index + " from " + message.peerId + " (" + message.issuerHostname + ")");
+ if (bitfield[message.index] == '0') {
+ piecesRequested--;
+ //Removing the piece from our piece list.
+ //TODO: It can not work, I should test it
+ if (!currentPieces.remove((Object)Integer.valueOf(message.index))) {
+ }
+ //Setting the fact that we have the piece
+ bitfield[message.index] = '1';
+ pieces++;
+ Msg.debug("My status is now " + getStatus());
+ //Sending the information to all the peers we are connected to
+ sendHave(message.index);
+ //sending UNINTERSTED to peers that doesn't have what we want.
+ updateInterestedAfterReceive();
+ }
+ else {
+ Msg.debug("However, we already have it.");
+ }
+ }
+ break;
+ }
+ }
+ /**
+ * Wait for the node to receive interesting bitfield messages (ie: non empty)
+ * to be received
+ */
+ void waitForPieces() {
+ boolean finished = false;
+ while (Msg.getClock() < deadline && !finished) {
+ if (commReceived == null) {
+ commReceived = Task.irecv(mailbox);
+ }
+ try {
+ commReceived.waitCompletion(Common.TIMEOUT_MESSAGE);
+ handleMessage(commReceived.getTask());
+ if (currentPiece != -1) {
+ finished = true;
+ }
+ commReceived = null;
+ }
+ catch (MsgException e) {
+ commReceived = null;
+ }
+ }
+ }
+
+ private boolean hasFinished() {
+ for (int i = 0; i < bitfield.length; i++) {
+ if (bitfield[i] == '1') {
+ return true;
+ }
+ }
+ return false;
+ }
+ /**
+ * Updates the list of who has a piece from a bitfield
+ * @param bitfield bitfield
+ */
+ private void updatePiecesCountFromBitfield(char bitfield[]) {
+ for (int i = 0; i < Common.FILE_PIECES; i++) {
+ if (bitfield[i] == '1') {
+ piecesCount[i]++;
+ }
+ }
+ }
+ /**
+ * Update the piece the peer is currently interested in.
+ * There is two cases (as described in "Bittorrent Architecture Protocol", Ryan Toole :
+ * If the peer has less than 3 pieces, he chooses a piece at random.
+ * If the peer has more than pieces, he downloads the pieces that are the less
+ * replicated
+ */
+ void updateCurrentPiece() {
+ if (currentPieces.size() >= (Common.FILE_PIECES - pieces)) {
+ return;
+ }
+ if (true || pieces < 3) {
+ int i = 0, peerPiece;
+ do {
+ currentPiece = ((int)Msg.getClock() + id + i) % Common.FILE_PIECES;
+ i++;
+ } while (!(bitfield[currentPiece] == '0' && !currentPieces.contains(currentPiece)));
+ }
+ else {
+ //trivial min algorithm.
+ //TODO
+ }
+ currentPieces.add(currentPiece);
+ Msg.debug("New interested piece: " + currentPiece);
+ assert currentPiece >= 0 && currentPiece < Common.FILE_PIECES;
+ }
+ /**
+ * Update the list of current choked and unchoked peers, using the
+ * choke algorithm
+ */
+ private void updateChokedPeers() {
+ round = (round + 1) % 3;
+ if (peers.size() == 0) {
+ return;
+ }
+ //remove a peer from the list
+ Iterator<Entry<Integer, Connection>> it = activePeers.entrySet().iterator();
+ if (it.hasNext()) {
+ Entry<Integer,Connection> e = it.next();
+ Connection peerChoked = e.getValue();
+ sendChoked(peerChoked.mailbox);
+ peerChoked.chokedUpload = true;
+ activePeers.remove(e.getKey());
+ }
+ //Random optimistic unchoking
+ if (round == 0 || true) {
+ int j = 0, i;
+ Connection peerChoosed = null;
+ do {
+ i = 0;
+ int idChosen = ((int)Msg.getClock() + j) % peers.size();
+ for (Connection connection : peers.values()) {
+ if (i == idChosen) {
+ peerChoosed = connection;
+ break;
+ }
+ i++;
+ } //TODO: Not really the best way ever
+ if (!peerChoosed.interested) {
+ peerChoosed = null;
+ }
+ j++;
+ } while (peerChoosed == null && j < Common.MAXIMUM_PAIRS);
+ if (peerChoosed != null) {
+ activePeers.put(peerChoosed.id,peerChoosed);
+ peerChoosed.chokedUpload = false;
+ sendUnchoked(peerChoosed.mailbox);
+ }
+ }
+ }
+ /**
+ * Updates our "interested" state about peers: send "not interested" to peers
+ * that don't have any more pieces we want.
+ */
+ private void updateInterestedAfterReceive() {
+ boolean interested;
+ for (Connection connection : peers.values()) {
+ interested = false;
+ if (connection.amInterested) {
+ for (Integer piece : currentPieces) {
+ if (connection.bitfield[piece] == '1') {
+ interested = true;
+ break;
+ }
+ }
+ if (!interested) {
+ connection.amInterested = false;
+ sendNotInterested(connection.mailbox);
+ }
+ }
+ }
+ }
+ /**
+ * Send request messages to a peer that have unchoked us
+ * @param remotePeer peer data to the peer we want to send the request
+ */
+ private void sendRequestsToPeer(Connection remotePeer) {
+ for (Integer piece : currentPieces) {
+ if (remotePeer.bitfield != null && remotePeer.bitfield[piece] == '1') {
+ sendRequest(remotePeer.mailbox, piece);
+ }
+ }
+ }
+ /**
+ * Find the peers that have the current interested piece and send them
+ * the "interested" message
+ */
+ private void sendInterestedToPeers() {
+ if (currentPiece == -1) {
+ return;
+ }
+ for (Connection connection : peers.values()) {
+ if (connection.bitfield != null && connection.bitfield[currentPiece] == '1' && !connection.amInterested) {
+ connection.amInterested = true;
+ MessageTask task = new MessageTask(MessageTask.Type.INTERESTED, hostname, this.mailbox, this.id);
+ task.dsend(connection.mailbox);
+ }
+ }
+ currentPiece = -1;
+ piecesRequested++;
+ }
+ /**
+ * Send a "interested" message to a peer.
+ */
+ private void sendInterested(String mailbox) {
+ MessageTask task = new MessageTask(MessageTask.Type.INTERESTED, hostname, this.mailbox, this.id);
+ task.dsend(mailbox);
+ }
+ /**
+ * Send a "not interested" message to a peer
+ * @param mailbox mailbox destination mailbox
+ */
+ private void sendNotInterested(String mailbox) {
+ MessageTask task = new MessageTask(MessageTask.Type.NOTINTERESTED, hostname, this.mailbox, this.id);
+ task.dsend(mailbox);
+ }
+ /**
+ * Send a handshake message to all the peers the peer has.
+ * @param peer peer data
+ */
+ private void sendHandshakeAll() {
+ for (Connection remotePeer : peers.values()) {
+ MessageTask task = new MessageTask(MessageTask.Type.HANDSHAKE, hostname, mailbox,
+ id);
+ task.dsend(remotePeer.mailbox);
+ }
+ }
+ /**
+ * Send a "handshake" message to an user
+ * @param mailbox mailbox where to we send the message
+ */
+ private void sendHandshake(String mailbox) {
+ Msg.debug("Sending a HANDSHAKE to " + mailbox);
+ MessageTask task = new MessageTask(MessageTask.Type.HANDSHAKE, hostname, this.mailbox, this.id);
+ task.dsend(mailbox);
+ }
+ /**
+ * Send a "choked" message to a peer
+ */
+ private void sendChoked(String mailbox) {
+ Msg.debug("Sending a CHOKE to " + mailbox);
+ MessageTask task = new MessageTask(MessageTask.Type.CHOKE, hostname, this.mailbox, this.id);
+ task.dsend(mailbox);
+ }
+ /**
+ * Send a "unchoked" message to a peer
+ */
+ private void sendUnchoked(String mailbox) {
+ Msg.debug("Sending a UNCHOKE to " + mailbox);
+ MessageTask task = new MessageTask(MessageTask.Type.UNCHOKE, hostname, this.mailbox, this.id);
+ task.dsend(mailbox);
+ }
+ /**
+ * Send a "HAVE" message to all peers we are connected to
+ */
+ private void sendHave(int piece) {
+ Msg.debug("Sending HAVE message to all my peers");
+ for (Connection remotePeer : peers.values()) {
+ MessageTask task = new MessageTask(MessageTask.Type.HAVE, hostname, this.mailbox, this.id, piece);
+ task.dsend(remotePeer.mailbox);
+ }
+ }
+ /**
+ * Send a bitfield message to all the peers the peer has.
+ * @param peer peer data
+ */
+ private void sendBitfield(String mailbox) {
+ Msg.debug("Sending a BITFIELD to " + mailbox);
+ MessageTask task = new MessageTask(MessageTask.Type.BITFIELD, hostname, this.mailbox, this.id, this.bitfield);
+ task.dsend(mailbox);
+ }
+ /**
+ * Send a "request" message to a pair, containing a request for a piece
+ */
+ private void sendRequest(String mailbox, int piece) {
+ Msg.debug("Sending a REQUEST to " + mailbox + " for piece " + piece);
+ MessageTask task = new MessageTask(MessageTask.Type.REQUEST, hostname, this.mailbox, this.id, piece);
+ task.dsend(mailbox);
+ }
+ /**
+ * Send a "piece" message to a pair, containing a piece of the file
+ */
+ private void sendPiece(String mailbox, int piece, boolean stalled) {
+ Msg.debug("Sending the PIECE " + piece + " to " + mailbox);
+ MessageTask task = new MessageTask(MessageTask.Type.PIECE, hostname, this.mailbox, this.id, piece, stalled);
+ task.dsend(mailbox);
+ }
+
+ private String getStatus() {
+ String s = "";
+ for (int i = 0; i < Common.FILE_PIECES; i++) {
+ s = s + bitfield[i];
+ }
+ return s;
+ }
+}
+
