netty入门——TimeServer和TimeClient

主要参考：

《netty权威指南》

http://netty.io/wiki/user-guide-for-4.x.html

当前没有处理tcp的拆包和粘包问题。

先简单的介绍一下netty，netty是一个高性能的网通通信框架。

以下摘自官网。

The Netty project  is an effort to provide an asynchronous event-driven network application framework and tooling for the rapid development of maintainable high-performance · high-scalability protocol servers and clients.

In other words, Netty is an NIO client server framework that enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server development.

从介绍上看，是因为netty的高性能和相对简单的开发框架，能够方便的开发出客户端和服务端，并且能够轻松的自定义通信协议。

首先是server端

package com.xueyou.demo.server;

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.NioEventLoop;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;

public class TimerServer {

    public void bind(int port) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 1024)
                    .childHandler(new ChildChannelHandler());

            ChannelFuture f = b.bind(port).sync();
            f.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    private class ChildChannelHandler extends ChannelInitializer<SocketChannel> {
        @Override
        protected void initChannel(SocketChannel socketChannel) throws Exception {
            socketChannel.pipeline().addLast(new TimeServerHandler());
        }
    }

    public static void main(String[] args) {
        int port = 56789;
        try {
            new TimerServer().bind(port);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
        }
    }
}

package com.xueyou.demo.server;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.util.ReferenceCountUtil;

import javax.sound.midi.Soundbank;
import java.util.Date;


public class TimeServerHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "UTF-8");
        System.out.println("The time server receive order:" + body);
//        String currentTime = "".equals(body) ? String.valueOf(new Date().getTime()) : "BAD ORDER\r\n";
        String currentTime = "ERROR";
        if (body.equals("abc\r\n")) {
            currentTime = String.valueOf(new Date().getTime());
        }
        ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
        ctx.write(resp);
        ctx.flush();
    }

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

然后是client端

package com.xueyou.demo.client;

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;

public class TimerClient {
    public void connect(int port, String host) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group).channel(NioSocketChannel.class)
                    .option(ChannelOption.SO_KEEPALIVE, true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            socketChannel.pipeline().addLast(new TimerClientHandler());
                        }
                    });
            ChannelFuture f = b.connect(host, port).sync();

            f.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }

    public static void main(String[] args) {
        int port = 56789;
        try {
            new TimerClient().connect(port, "localhost");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
        }
    }
}

package com.xueyou.demo.client;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

import java.util.concurrent.TimeUnit;

public class TimerClientHandler extends ChannelInboundHandlerAdapter {
    private final ByteBuf firstMessage;

    public TimerClientHandler() {
        byte[] req = "abc\r\n".getBytes();
        this.firstMessage = Unpooled.buffer(req.length);
        firstMessage.writeBytes(req);
    }

    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(firstMessage);
    }

    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "UTF-8");
        System.out.println("now is :" + body);
    }

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

当我们进行测试的时候可以通过Telnet进行，通过telnet发送数据给我们的server，然后看server得反应。

下面是运行结果：

服务端：

客户端：