Netty入门（一）-- 客户端示例

前言

　　本文主要实现基于Netty实现客户端，向服务器定时发送数据

如下为一个简单的Netty实例，本实例主要描述了Client向服务端定时发送数据，并实现重连机制及轮询发送数据

先直接上代码，后续在整理一些用法相关知识

例子中如有误，欢迎各位指正

1、pom.xml

        <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>4.1.36.Final</version>
        </dependency>

  2、NettyClient.java：主要为初始化Client Socket

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.util.CharsetUtil;


public class NettyClientTest implements Runnable{

    private static volatile EventLoopGroup workerGroup;

    private String ip;

    private int port;

    public NettyClientTest(String ip, int port) {
        this.ip = ip;
        this.port = port;
    }

    @Override
    public void run() {
        // 客户端的配置
        workerGroup= new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(workerGroup)
                    .channel(NioSocketChannel.class)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .handler(new ChannelInitializer() {
                        @Override
                        protected void initChannel(Channel channel) throws Exception {
                            ChannelPipeline p = channel.pipeline();
                            //编码格式
                            p.addLast("decoder", new StringDecoder(CharsetUtil.UTF_8))
                                    .addLast("encoder", new StringEncoder(CharsetUtil.UTF_8))
                                    //具体的客户端实现操作类
                                    .addLast(new NettyClientHandlerTest(bootstrap, ip, port));
                        }
                    });

            ChannelFuture future = null;
            /**
             *防止初次链接不上 每隔十秒重连一次
             */
            while (future == null || !future.isSuccess()) {
                try {
                    future = bootstrap.connect(ip, port).sync();
                } catch (Exception ex) {
                    System.out.println("重连中。。。。");
                    Thread.sleep(10000);
                }
            }


            future.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            //workerGroup.shutdownGracefully();
        }
    }



    public static void main(String[] args) {

        //开启单条条线程，每条线程就相当于一个客户端
        new NettyClientTest("localhost",10002).run();
    }
}

    3、NettyClientHandlerTest.java：配合NettyClient，完成消息的读取操作以及业务处理。

　　

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import java.net.InetSocketAddress;
import java.util.concurrent.TimeUnit;



public class NettyClientHandlerTest extends ChannelInboundHandlerAdapter{

    /**
     *
     */
    private final Bootstrap bootstrap;

    /**
     * 交互channel
     */
    private static Channel channel;

    /**
     * 服务端ip  重连时使用
     */
    private String ip;

    /**
     * 服务端端口
     */
    private int port;


    /**
     * 断线重连等待时间 /S
     */
    private final static int reconnectDelay = 10;

    public NettyClientHandlerTest(Bootstrap bootstrap, String ip, int port) {
        this.bootstrap = bootstrap;
        this.ip = ip;
        this.port = port;
    }

    /**
     * 客户端连接服务器后被调用
     * @param ctx
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        channel = ctx.channel();
        ctx.fireChannelActive();
        channelWrite();
    }

    /**
     * @param ctx
     * @DESCRIPTION: 服务端端终止连接 后触发此函数
     * @return: void
     */
    @Override
    public void channelInactive(ChannelHandlerContext ctx) {

        ctx.fireChannelInactive();
        System.out.println("服务端终止了服务");
        try {
            super.channelInactive(ctx);
        } catch (Exception e) {
            e.printStackTrace();
        }
        //断开连接后实现重连机制
        ctx.channel().eventLoop().schedule(() -> doConnect(), reconnectDelay, TimeUnit.SECONDS);
    }

    /**
     * 每隔十秒重连一次
     */
    private void doConnect() {
        ChannelFuture future = bootstrap.connect(new InetSocketAddress(ip, port));
        future.addListener(new ChannelFutureListener() {
            public void operationComplete(ChannelFuture f) throws Exception {
                if (f.isSuccess()) {
                    System.out.println("Started Tcp Client: ");
                } else {
                    System.out.println("Started Tcp Client Failed: ");
                    f.channel().eventLoop().schedule(() -> doConnect(), reconnectDelay, TimeUnit.SECONDS);
                }
            }
        });
    }

    /**
     * 从服务器接收到数据后调用
     * @param ctx
     * @param msg
     */
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {

        System.out.println("回写数据:" + msg);
    }


    /**
     * 发生异常时被调用
     * @param ctx
     * @param cause
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {

        //cause.printStackTrace();
        System.out.println("服务端发生异常【" + cause.getMessage() + "】");
        ctx.close();
    }

    /**
     * 新启一个线程  轮询发送数据
     * @DESCRIPTION: 客户端给服务端发送消息
     * @return: void
     */
    public void channelWrite() {
        new Thread(new DataSendTest(channel)).start();
    }
}

   4、DataSendTest.java：数据发送处理

　　

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;


public class DataSendTest implements Runnable{

    /**
     * 与服务端交互的通道
     */
    private Channel channel;

    public DataSendTest(Channel channel){
        this.channel = channel;
    }

    /**
     * 轮询发送数据
     */
    @Override
    public void run() {
        while (true) {
            try{
                //channel通道关闭时  不发送数据
                if (!channel.isActive()) {
                    break;
                }
                byte[] bytes = new byte[]{10,12,13};
                ByteBuf byteBuf = Unpooled.wrappedBuffer(bytes);

                channel.write(byteBuf);
                channel.flush();

                Thread.sleep(1000);
            } catch (Exception ex) {

            }
        }
    }
}