Java tutorial
/** * Copyright (C) 2011-2012 Turn, Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.bittorrent.mpetazzoni.client; import com.bittorrent.mpetazzoni.common.Torrent; import com.bittorrent.mpetazzoni.client.peer.SharingPeer; import java.io.IOException; import java.net.InetAddress; import java.net.InetSocketAddress; import java.net.Socket; import java.net.SocketTimeoutException; import java.nio.ByteBuffer; import java.nio.channels.ServerSocketChannel; import java.nio.channels.SocketChannel; import java.text.ParseException; import java.util.Arrays; import java.util.HashSet; import java.util.Set; import java.util.concurrent.ExecutorService; import java.util.concurrent.LinkedBlockingQueue; import java.util.concurrent.ThreadFactory; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; import org.apache.commons.io.IOUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * Incoming peer connections service. * * <p> * Every BitTorrent client, BitTorrent being a peer-to-peer protocol, listens * on a port for incoming connections from other peers sharing the same * torrent. * </p> * * <p> * This ConnectionHandler implements this service and starts a listening socket * in the first available port in the default BitTorrent client port range * 6881-6889. When a peer connects to it, it expects the BitTorrent handshake * message, parses it and replies with our own handshake. * </p> * * <p> * Outgoing connections to other peers are also made through this service, * which handles the handshake procedure with the remote peer. Regardless of * the direction of the connection, once this handshake is successful, all * {@link IncomingConnectionListener}s are notified and passed the connected * socket and the remote peer ID. * </p> * * <p> * This class does nothing more. All further peer-to-peer communication happens * in the {@link com.bittorrent.mpetazzoni.client.peer.PeerExchange PeerExchange} * class. * </p> * * @author mpetazzoni * @see <a href="http://wiki.theory.org/BitTorrentSpecification#Handshake">BitTorrent handshake specification</a> */ public class ConnectionHandler implements Runnable { private static final Logger logger = LoggerFactory.getLogger(ConnectionHandler.class); public static final int PORT_RANGE_START = 6881; public static final int PORT_RANGE_END = 6889; private static final int OUTBOUND_CONNECTIONS_POOL_SIZE = 20; private static final int OUTBOUND_CONNECTIONS_THREAD_KEEP_ALIVE_SECS = 10; private static final int CLIENT_KEEP_ALIVE_MINUTES = 3; private SharedTorrent torrent; private String id; private ServerSocketChannel channel; private InetSocketAddress address; private Set<IncomingConnectionListener> listeners; private ExecutorService executor; private Thread thread; private boolean stop; /** * Create and start a new listening service for out torrent, reporting * with our peer ID on the given address. * * <p> * This binds to the first available port in the client port range * PORT_RANGE_START to PORT_RANGE_END. * </p> * * @param torrent The torrent shared by this client. * @param id This client's peer ID. * @param address The address to bind to. * @throws IOException When the service can't be started because no port in * the defined range is available or usable. */ ConnectionHandler(SharedTorrent torrent, String id, InetAddress address) throws IOException { this.torrent = torrent; this.id = id; // Bind to the first available port in the range // [PORT_RANGE_START; PORT_RANGE_END]. for (int port = ConnectionHandler.PORT_RANGE_START; port <= ConnectionHandler.PORT_RANGE_END; port++) { InetSocketAddress tryAddress = new InetSocketAddress(address, port); try { this.channel = ServerSocketChannel.open(); this.channel.socket().bind(tryAddress); this.channel.configureBlocking(false); this.address = tryAddress; break; } catch (IOException ioe) { // Ignore, try next port logger.warn("Could not bind to {}, trying next port...", tryAddress); } } if (this.channel == null || !this.channel.socket().isBound()) { throw new IOException("No available port for the BitTorrent client!"); } logger.info("Listening for incoming connections on {}.", this.address); this.listeners = new HashSet<IncomingConnectionListener>(); this.executor = null; this.thread = null; } /** * Return the full socket address this service is bound to. */ public InetSocketAddress getSocketAddress() { return this.address; } /** * Register a new incoming connection listener. * * @param listener The listener who wants to receive connection * notifications. */ public void register(IncomingConnectionListener listener) { this.listeners.add(listener); } /** * Start accepting new connections in a background thread. */ public void start() { if (this.channel == null) { throw new IllegalStateException("Connection handler cannot be recycled!"); } this.stop = false; if (this.executor == null || this.executor.isShutdown()) { this.executor = new ThreadPoolExecutor(OUTBOUND_CONNECTIONS_POOL_SIZE, OUTBOUND_CONNECTIONS_POOL_SIZE, OUTBOUND_CONNECTIONS_THREAD_KEEP_ALIVE_SECS, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(), new ConnectorThreadFactory()); } if (this.thread == null || !this.thread.isAlive()) { this.thread = new Thread(this); this.thread.setName("bt-serve"); this.thread.start(); } } /** * Stop accepting connections. * * <p> * <b>Note:</b> the underlying socket remains open and bound. * </p> */ public void stop() { this.stop = true; if (this.thread != null && this.thread.isAlive()) { try { this.thread.join(); } catch (InterruptedException ie) { Thread.currentThread().interrupt(); } } if (this.executor != null && !this.executor.isShutdown()) { this.executor.shutdownNow(); } this.executor = null; this.thread = null; } /** * Close this connection handler to release the port it is bound to. * * @throws IOException If the channel could not be closed. */ public void close() throws IOException { if (this.channel != null) { this.channel.close(); this.channel = null; } } /** * The main service loop. * * <p> * The service waits for new connections for 250ms, then waits 100ms so it * can be interrupted. * </p> */ @Override public void run() { while (!this.stop) { try { SocketChannel client = this.channel.accept(); if (client != null) { this.accept(client); } } catch (SocketTimeoutException ste) { // Ignore and go back to sleep } catch (IOException ioe) { logger.warn("Unrecoverable error in connection handler", ioe); this.stop(); } try { Thread.sleep(100); } catch (InterruptedException ie) { Thread.currentThread().interrupt(); } } } /** * Return a human-readable representation of a connected socket channel. * * @param channel The socket channel to represent. * @return A textual representation (<em>host:port</em>) of the given * socket. */ private String socketRepr(SocketChannel channel) { Socket s = channel.socket(); return String.format("%s:%d%s", s.getInetAddress().getHostName(), s.getPort(), channel.isConnected() ? "+" : "-"); } /** * Accept the next incoming connection. * * <p> * When a new peer connects to this service, wait for it to send its * handshake. We then parse and check that the handshake advertises the * torrent hash we expect, then reply with our own handshake. * </p> * * <p> * If everything goes according to plan, notify the * <code>IncomingConnectionListener</code>s with the connected socket and * the parsed peer ID. * </p> * * @param client The accepted client's socket channel. */ private void accept(SocketChannel client) throws IOException, SocketTimeoutException { try { logger.debug("New incoming connection, waiting for handshake..."); Handshake hs = this.validateHandshake(client, null); int sent = this.sendHandshake(client); logger.trace("Replied to {} with handshake ({} bytes).", this.socketRepr(client), sent); // Go to non-blocking mode for peer interaction client.configureBlocking(false); client.socket().setSoTimeout(CLIENT_KEEP_ALIVE_MINUTES * 60 * 1000); this.fireNewPeerConnection(client, hs.getPeerId()); } catch (ParseException pe) { logger.info("Invalid handshake from {}: {}", this.socketRepr(client), pe.getMessage()); IOUtils.closeQuietly(client); } catch (IOException ioe) { logger.warn("An error occured while reading an incoming " + "handshake: {}", ioe.getMessage()); if (client.isConnected()) { IOUtils.closeQuietly(client); } } } /** * Tells whether the connection handler is running and can be used to * handle new peer connections. */ public boolean isAlive() { return this.executor != null && !this.executor.isShutdown() && !this.executor.isTerminated(); } /** * Connect to the given peer and perform the BitTorrent handshake. * * <p> * Submits an asynchronous connection task to the outbound connections * executor to connect to the given peer. * </p> * * @param peer The peer to connect to. */ public void connect(SharingPeer peer) { if (!this.isAlive()) { throw new IllegalStateException("Connection handler is not accepting new peers at this time!"); } this.executor.submit(new ConnectorTask(this, peer)); } /** * Validate an expected handshake on a connection. * * <p> * Reads an expected handshake message from the given connected socket, * parses it and validates that the torrent hash_info corresponds to the * torrent we're sharing, and that the peerId matches the peer ID we expect * to see coming from the remote peer. * </p> * * @param channel The connected socket channel to the remote peer. * @param peerId The peer ID we expect in the handshake. If <em>null</em>, * any peer ID is accepted (this is the case for incoming connections). * @return The validated handshake message object. */ private Handshake validateHandshake(SocketChannel channel, byte[] peerId) throws IOException, ParseException { ByteBuffer len = ByteBuffer.allocate(1); ByteBuffer data; // Read the handshake from the wire logger.trace("Reading handshake size (1 byte) from {}...", this.socketRepr(channel)); if (channel.read(len) < len.capacity()) { throw new IOException("Handshake size read underrrun"); } len.rewind(); int pstrlen = len.get(); data = ByteBuffer.allocate(Handshake.BASE_HANDSHAKE_LENGTH + pstrlen); data.put((byte) pstrlen); int expected = data.remaining(); int read = channel.read(data); if (read < expected) { throw new IOException("Handshake data read underrun (" + read + " < " + expected + " bytes)"); } // Parse and check the handshake data.rewind(); Handshake hs = Handshake.parse(data); if (!Arrays.equals(hs.getInfoHash(), this.torrent.getInfoHash())) { throw new ParseException("Handshake for unknow torrent " + Torrent.byteArrayToHexString(hs.getInfoHash()) + " from " + this.socketRepr(channel) + ".", pstrlen + 9); } if (peerId != null && !Arrays.equals(hs.getPeerId(), peerId)) { throw new ParseException( "Announced peer ID " + Torrent.byteArrayToHexString(hs.getPeerId()) + " did not match expected peer ID " + Torrent.byteArrayToHexString(peerId) + ".", pstrlen + 29); } return hs; } /** * Send our handshake message to the socket. * * @param channel The socket channel to the remote peer. */ private int sendHandshake(SocketChannel channel) throws IOException { return channel.write( Handshake.craft(this.torrent.getInfoHash(), this.id.getBytes(Torrent.BYTE_ENCODING)).getData()); } /** * Trigger the new peer connection event on all registered listeners. * * @param channel The socket channel to the newly connected peer. * @param peerId The peer ID of the connected peer. */ private void fireNewPeerConnection(SocketChannel channel, byte[] peerId) { for (IncomingConnectionListener listener : this.listeners) { listener.handleNewPeerConnection(channel, peerId); } } private void fireFailedConnection(SharingPeer peer, Throwable cause) { for (IncomingConnectionListener listener : this.listeners) { listener.handleFailedConnection(peer, cause); } } /** * A simple thread factory that returns appropriately named threads for * outbound connector threads. * * @author mpetazzoni */ private static class ConnectorThreadFactory implements ThreadFactory { private int number = 0; @Override public Thread newThread(Runnable r) { Thread t = new Thread(r); t.setName("bt-connect-" + ++this.number); return t; } } /** * An outbound connection task. * * <p> * These tasks are fed to the thread executor in charge of processing * outbound connection requests. It attempts to connect to the given peer * and proceeds with the BitTorrent handshake. If the handshake is * successful, the new peer connection event is fired to all incoming * connection listeners. Otherwise, the failed connection event is fired. * </p> * * @author mpetazzoni */ private static class ConnectorTask implements Runnable { private final ConnectionHandler handler; private final SharingPeer peer; private ConnectorTask(ConnectionHandler handler, SharingPeer peer) { this.handler = handler; this.peer = peer; } @Override public void run() { InetSocketAddress address = new InetSocketAddress(this.peer.getIp(), this.peer.getPort()); SocketChannel channel = null; try { logger.info("Connecting to {}...", this.peer); channel = SocketChannel.open(address); while (!channel.isConnected()) { Thread.sleep(10); } logger.debug("Connected. Sending handshake to {}...", this.peer); channel.configureBlocking(true); int sent = this.handler.sendHandshake(channel); logger.debug("Sent handshake ({} bytes), waiting for response...", sent); Handshake hs = this.handler.validateHandshake(channel, (this.peer.hasPeerId() ? this.peer.getPeerId().array() : null)); logger.info("Handshaked with {}, peer ID is {}.", this.peer, Torrent.byteArrayToHexString(hs.getPeerId())); // Go to non-blocking mode for peer interaction channel.configureBlocking(false); this.handler.fireNewPeerConnection(channel, hs.getPeerId()); } catch (Exception e) { if (channel != null && channel.isConnected()) { IOUtils.closeQuietly(channel); } this.handler.fireFailedConnection(this.peer, e); } } } }