Netty入门介绍

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public class EchoServerHandler extends SimpleChannelUpstreamHandler {

    private static final Logger logger = Logger.getLogger(
            EchoServerHandler.class.getName());

    private final AtomicLong transferredBytes = new AtomicLong();

    public long getTransferredBytes() {
        return transferredBytes.get();
    }

    @Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
        // Send back the received message to the remote peer.
        transferredBytes.addAndGet(((ChannelBuffer) e.getMessage()).readableBytes());
        e.getChannel().write(e.getMessage());
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
        // Close the connection when an exception is raised.
        logger.log(Level.WARNING, "Unexpected exception from downstream.", e.getCause());
        e.getChannel().close();
    }
}


public class EchoServer {

    private final int port;

    public EchoServer(int port) {
        this.port = port;
    }

    public void run() {
        // Configure the server.
        ServerBootstrap bootstrap = new ServerBootstrap(
                new NioServerSocketChannelFactory(
                        Executors.newCachedThreadPool(),
                        Executors.newCachedThreadPool()));

        // Set up the pipeline factory.
        bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
            public ChannelPipeline getPipeline() throws Exception {
                return Channels.pipeline(new EchoServerHandler());
            }
        });

        // Bind and start to accept incoming connections.
        bootstrap.bind(new InetSocketAddress(port));
    }

    public static void main(String[] args) throws Exception {
        int port;
        if (args.length > 0) {
            port = Integer.parseInt(args[0]);
        } else {
            port = 8080;
        }
        new EchoServer(port).run();
    }
}


public class EchoClientHandler extends SimpleChannelUpstreamHandler {

    private static final Logger logger = Logger.getLogger(
            EchoClientHandler.class.getName());

    private final ChannelBuffer firstMessage;
    private final AtomicLong transferredBytes = new AtomicLong();

    /**
     * Creates a client-side handler.
     */
    public EchoClientHandler(int firstMessageSize) {
        if (firstMessageSize <= 0) {
            throw new IllegalArgumentException("firstMessageSize: " + firstMessageSize);
        }
        firstMessage = ChannelBuffers.buffer(firstMessageSize);
        for (int i = 0; i < firstMessage.capacity(); i ++) {
            firstMessage.writeByte((byte) i);
        }
    }

    public long getTransferredBytes() {
        return transferredBytes.get();
    }

    @Override
    public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) {
        // Send the first message.  Server will not send anything here
        // because the firstMessage's capacity is 0.
        e.getChannel().write(firstMessage);
    }

    @Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
        // Send back the received message to the remote peer.
        transferredBytes.addAndGet(((ChannelBuffer) e.getMessage()).readableBytes());
        e.getChannel().write(e.getMessage());
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
        // Close the connection when an exception is raised.
        logger.log( Level.WARNING,"Unexpected exception from downstream.",e.getCause());
        e.getChannel().close();
    }
}

public class EchoClient {

    private final String host;
    private final int port;
    private final int firstMessageSize;

    public EchoClient(String host, int port, int firstMessageSize) {
        this.host = host;
        this.port = port;
        this.firstMessageSize = firstMessageSize;
    }

    public void run() {
        // Configure the client.
        ClientBootstrap bootstrap = new ClientBootstrap(
                new NioClientSocketChannelFactory(
                        Executors.newCachedThreadPool(),
                        Executors.newCachedThreadPool()));

        // Set up the pipeline factory.
        bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
            public ChannelPipeline getPipeline() throws Exception {
                return Channels.pipeline(
                        new EchoClientHandler(firstMessageSize));
            }
        });

        // Start the connection attempt.
        ChannelFuture future = bootstrap.connect(new InetSocketAddress(host, port));

        // Wait until the connection is closed or the connection attempt fails.
        future.getChannel().getCloseFuture().awaitUninterruptibly();

        // Shut down thread pools to exit.
        bootstrap.releaseExternalResources();
    }

    public static void main(String[] args) throws Exception {
        // Print usage if no argument is specified.
        if (args.length < 2 || args.length > 3) {
            System.err.println("Usage: " + EchoClient.class.getSimpleName() +" <host> <port> [<first message size>]");
            return;
        }

        // Parse options.
        final String host = args[0];
        final int port = Integer.parseInt(args[1]);
        final int firstMessageSize;
        if (args.length == 3) {
            firstMessageSize = Integer.parseInt(args[2]);
        } else {
            firstMessageSize = 256;
        }

        new EchoClient(host, port, firstMessageSize).run();
    }
}