Netty基础入门学习

<dependency>
  <groupId>io.netty</groupId>
  <artifactId>netty-all</artifactId>
  <version>4.1.31.Final</version>
</dependency>

package com.netty.hanler;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.util.ReferenceCountUtil;
/**
 * Created by Janus on 2018/11/19.
 */
public class DiscardServerHandler extends ChannelInboundHandlerAdapter {// (1)
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) { // (2)
        // Discard the received data silently.
        try {
            ((ByteBuf) msg).release(); // (3)
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            ReferenceCountUtil.release(msg);
        }
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { // (4)
        // Close the connection when an exception is raised.
        cause.printStackTrace();
        ctx.close();
    }
}

package com.netty.server;
import com.netty.hanler.DiscardServerHandler;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
/**
 * Created by Janus on 2018/11/19.
 */
public class DiscardServer {
    private int port;
    public DiscardServer(int port) {
        this.port = port;
    }
    public void run() throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup(); // (1)
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap(); // (2)
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class) // (3)
                    .childHandler(new ChannelInitializer<SocketChannel>() { // (4)
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(new DiscardServerHandler());
                        }
                    })
                    .option(ChannelOption.SO_BACKLOG, 128)          // (5)
                    .childOption(ChannelOption.SO_KEEPALIVE, true); // (6)
            // Bind and start to accept incoming connections.
            //绑定端口，同步等待成功
            ChannelFuture f = b.bind(port).sync(); // (7)
            // Wait until the server socket is closed.
            // In this example, this does not happen, but you can do that to gracefully
            // shut down your server.
            //等待服务器端监听端口关闭
            f.channel().closeFuture().sync();
        } finally {
        //优雅退出，释放线程池资源
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
        }
    }
    public static void main(String[] args) throws Exception {
        int port = 8080;
        if (args.length > 0) {
            port = Integer.parseInt(args[0]);
        }
        new DiscardServer(port).run();
    }
}

   @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) { // (2)
        // Discard the received data silently.
        ByteBuf in = (ByteBuf) msg;
        try {
            while (in.isReadable()) { // (1)
                System.out.print((char) in.readByte());
                System.out.flush();
            }
        } finally {
            ReferenceCountUtil.release(msg); // (2)
        }
    }

f.addListener(ChannelFutureListener.CLOSE);

$ rdate -o <port> -p <host>

import com.netty.hanler.TimeClientHandler;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
/**
 * Created by Janus on 2018/11/19.
 */
public class TimeClient {
    public static void main(String[] args) throws Exception {
//        String host = args[0];
//        int port = Integer.parseInt(args[1]);
        String host="localhost";
        //端口与Server保持一致
        int port=8080;
        // 这里只有一个workerGroup 
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap(); // (1)
            b.group(workerGroup); // (2)
            //这里为NioSocketChannel not NioServerSocketChannel
            b.channel(NioSocketChannel.class); // (3)
            b.option(ChannelOption.SO_KEEPALIVE, true); // (4)
            b.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                public void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new TimeClientHandler());
                }
            });
            // Start the client.
            ChannelFuture f = b.connect(host, port).sync(); // (5)
            // Wait until the connection is closed.
            f.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
        }
    }
}

public class TimeClientHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        ByteBuf m = (ByteBuf) msg; // (1)
        try {
            long currentTimeMillis = (m.readUnsignedInt() - 2208988800L) * 1000L;
            System.out.println(new Date(currentTimeMillis));
            ctx.close();
        } finally {
            m.release();
        }
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

public class TimeDecoder extends ByteToMessageDecoder { // (1)
    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) { // (2)
        if (in.readableBytes() < 4) {
            return; // (3)
        }
        out.add(in.readBytes(4)); // (4)
    }
}

b.handler(new ChannelInitializer<SocketChannel>() {
    @Override
    public void initChannel(SocketChannel ch) throws Exception {
        ch.pipeline().addLast(new TimeDecoder(),new TimeClientHandler());
    }
});

public class TimeDecoder extends ReplayingDecoder<Void> {
    @Override
    protected void decode(
            ChannelHandlerContext ctx, ByteBuf in, List<Object> out) {
        out.add(in.readBytes(4));
    }
}

public class UnixTime {
    private final long value;
    public UnixTime() {
        this(System.currentTimeMillis() / 1000L + 2208988800L);
    }
    public UnixTime(long value) {
        this.value = value;
    }
    public long value() {
        return value;
    }
    @Override
    public String toString() {
        return new Date((value() - 2208988800L) * 1000L).toString();
    }
}

public class TimeDecoder extends ByteToMessageDecoder { // (1)
    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) { // (2)
        System.out.println("进入TimeDecoder.decode方法");
        if (in.readableBytes() < 4) {
            System.out.println("Bytes is not reach 4");
            return; // (3)
        }
//        out.add(in.readBytes(4)); // (4)
        out.add(new UnixTime(in.readUnsignedInt())); // (4)
    }
}

  @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        UnixTime m = (UnixTime) msg;
        System.out.println(m);
        ctx.close();
    }

   @Override
    public void channelActive(ChannelHandlerContext ctx) {
        ChannelFuture f = ctx.writeAndFlush(new UnixTime());
        f.addListener(ChannelFutureListener.CLOSE);
    }

public class TimeEncoder extends ChannelOutboundHandlerAdapter {
    @Override
    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
        UnixTime m = (UnixTime) msg;
        ByteBuf encoded = ctx.alloc().buffer(4);
        encoded.writeInt((int)m.value());
        ctx.write(encoded, promise); // (1)
    }
}

public class TimeEncoder extends MessageToByteEncoder<UnixTime> {
    @Override
    protected void encode(ChannelHandlerContext ctx, UnixTime msg, ByteBuf out) {
        out.writeInt((int)msg.value());
    }
}

b.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class) // (3)
.childHandler(new ChannelInitializer<SocketChannel>() { // (4)
  @Override
  public void initChannel(SocketChannel ch) throws Exception {
  ch.pipeline().addLast(new TimeEncoder(),new TimeServerHandler());
  }
})
.option(ChannelOption.SO_BACKLOG, 128)          // (5)
.childOption(ChannelOption.SO_KEEPALIVE, true); // (6)

workerGroup.shutdownGracefully();
bossGroup.shutdownGracefully();