《精通并发与Netty》学习笔记（03 - 客户端程序编写）

上节我们编写了netty服务端的程序，这节我们来写客户端程序

第一步：编写客户端主程序MyClient

package com.ssy.netty.demo01;

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

public class MyClient {
    public static void main(String[] args) {
        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(eventLoopGroup) // 绑定线程池
                    .channel(NioSocketChannel.class)
                    .handler(new MyClientInitializer());

            //绑定端口号
            ChannelFuture channelFuture = bootstrap.bind(8888).sync();
            channelFuture.channel().closeFuture().sync();
        } catch (Exception e) {
            eventLoopGroup.shutdownGracefully();
        }
    }
}

第二步：编写MyClientInitializer

package com.ssy.netty.demo01;

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.codec.LengthFieldPrepender;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.util.CharsetUtil;

public class MyClientInitializer  extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE,0,4,0,4));
        pipeline.addLast(new LengthFieldPrepender(4));
        pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
        pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
        pipeline.addLast(new MyClientHandler());
    }
}

第三步：编写MyClientHandler

package com.ssy.netty.demo01;

import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.HttpObject;
import io.netty.util.concurrent.EventExecutorGroup;

import java.time.LocalDateTime;

public class MyClientHandler extends SimpleChannelInboundHandler<String> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println(ctx.channel().remoteAddress());
        System.out.println("client output:"+msg);
        ctx.writeAndFlush("from client" + LocalDateTime.now());
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}

到此为止，我们已经完成了简单的netty服务端与客户端的通信程序，下节我们会对谷歌的Google Protobuf做一次详解，敬请期待吧！