Netty 框架基本流程

服务端

package com.mypractice.netty.server;

import java.net.InetSocketAddress;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;

public class EchoServer {
    private final int port;

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

    public static void main(String[] args) throws Exception {

        int port = Integer.parseInt("8888"); 
        new EchoServer(port).start();    
    }

    public void start() throws Exception {
        EventLoopGroup boss = new NioEventLoopGroup();
        EventLoopGroup worker = new NioEventLoopGroup();
        try {
             ServerBootstrap b = new ServerBootstrap();    
             b.group(boss,worker)
                 .channel(NioServerSocketChannel.class) 
                 .localAddress(new InetSocketAddress(port)) 
                 .childHandler(new CostomServerChannelInitializer())
                 //设置高低水位
                 .childOption(ChannelOption.WRITE_BUFFER_LOW_WATER_MARK, 1)
                 .childOption(ChannelOption.WRITE_BUFFER_HIGH_WATER_MARK, 4);
        
            //绑定监听 
            ChannelFuture f = b.bind().sync();
            System.out.println("正在监听...");
            f.channel().closeFuture().sync();    
        } finally {
            //关闭EventLoopGroup，释放资源
            boss.shutdownGracefully().sync();    
            worker.shutdownGracefully().sync();    
        }
    }
}

package com.mypractice.netty.server;

import io.netty.channel.ChannelInitializer;
import io.netty.channel.socket.SocketChannel;

public class CostomServerChannelInitializer extends ChannelInitializer<SocketChannel> {

    protected void initChannel(SocketChannel ch) throws Exception {
        // EchoServerHandler被标注为@Shareable，所以我们可以总是使用同样的实例
        ch.pipeline().addLast(new EchoServerHandler());
    }

}

package com.mypractice.netty.server;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelOption;
import io.netty.util.CharsetUtil;

public class EchoServerHandler extends ChannelInboundHandlerAdapter {

@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
System.out.println("Server 受到client连接："+ctx.toString());
System.out.println(ctx.channel().config().getWriteBufferHighWaterMark());
System.out.println(ctx.channel().config().getWriteBufferLowWaterMark());
int size = ctx.channel().unsafe().outboundBuffer().size();
System.out.println("size1:" + size);
super.channelActive(ctx);
}
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {
ByteBuf in = (ByteBuf) msg;
in.writeBytes("hello iam client".getBytes());
System.out.println("Server received: " + in.toString(CharsetUtil.UTF_8)); 
ctx.write(in); 
}

@Override
public void channelReadComplete(ChannelHandlerContext ctx) {
ctx.writeAndFlush(Unpooled.EMPTY_BUFFER)
.addListener(ChannelFutureListener.CLOSE);//将未决消息冲刷到远程节点，并且关闭该Channel
}
@Override
public void channelWritabilityChanged(ChannelHandlerContext ctx) throws Exception {
// TODO Auto-generated method stub
System.out.println("channge:" +ctx.channel().isWritable());
int size = ctx.channel().unsafe().outboundBuffer().size();
System.out.println("size:" + size);
super.channelWritabilityChanged(ctx);
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx,
Throwable cause) {
cause.printStackTrace(); 
ctx.close();
}
}

客户端

package com.mypractice.netty.client;

import java.net.InetSocketAddress;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;

public class EchoClient {
    private final String host;
    private final int port;

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

    public void start() throws Exception {
        EventLoopGroup worker = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(worker)
            .channel(NioSocketChannel.class)
            .remoteAddress(new InetSocketAddress(host, port))
            .handler(new CostomChannelInitializer());
            
            ChannelFuture f = b.connect().sync(); // 连接到远程节点，阻塞等待直到连接完成
            f.channel().closeFuture().sync(); // 阻塞，直到Channel关闭
            System.out.println("client close");
        } finally {
            worker.shutdownGracefully().sync(); // 关闭线程池并且释放所有的资源
        }
    }

    public static void main(String[] args) throws Exception {
        // if (args.length != 2) {
        // System.err.println(
        // "Usage: " + EchoClient.class.getSimpleName() +
        // " <host> <port>");
        // return;
        // }

        String host = "127.0.0.1";// args[0];
        int port = 8888;// Integer.parseInt(args[1]);
        new EchoClient(host, port).start();
    }
}

package com.mypractice.netty.client;


import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;

public class CostomChannelInitializer extends ChannelInitializer<SocketChannel> {

    @Override
    protected void initChannel(SocketChannel sc) throws Exception {
        ChannelPipeline pipeline = sc.pipeline();
        pipeline.addLast(new EchoClientHandler());
    }

}

package com.mypractice.netty.client;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.util.CharsetUtil;

//@Sharable     //⇽---  标记该类的实例可以被多个Channel共享
public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {
    /**
     * 收到链接时出发
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        System.out.println("rock!");
        ctx.writeAndFlush(Unpooled.copiedBuffer("Netty rocks!",    // ⇽---  当被通知Channel是活跃的时候，发送一条消息
        CharsetUtil.UTF_8));
    }
    /**
     * 收到数据时触发
     */
    @Override
    public void channelRead0(ChannelHandlerContext ctx, ByteBuf in) {
        System.out.println("Client received: " + in.toString(CharsetUtil.UTF_8));
    }
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        // TODO Auto-generated method stub
        ByteBuf in = (ByteBuf) msg;
        System.out.println("Client ##received: " + in.toString(CharsetUtil.UTF_8));
        super.channelRead(ctx, msg);
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, //    ⇽---  在发生异常时，记录错误并关闭Channel 
        Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}