一、netty初学，简单的echo服务器，客户端

无论服务器还是客户端都是由下面两步组成

1、ChannelHandler 用与处理各种事件的逻辑处理。决定了连接创建后和接收到信息后该如何处理。

直接或简接要实现ChannelInboundHandler 接口.

2、Bootstrap启动服务器或客户端服务器用 ServerBootstrap 客户端用 BootStrap。

pom

<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.0.29.Final</version>
</dependency>

EchoServerChannelHandler

package test01;

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.util.CharsetUtil;

/**

* Created by wujiazhen on 2018/1/15.

public class EchoServerChannelHandler extends ChannelInboundHandlerAdapter {

@Override

public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {

ByteBuf in = (ByteBuf)msg;

System. out .println( "server receive:" +in.toString(CharsetUtil. UTF_8 ));

ctx.write(msg);

}

@Override

public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {

ctx.writeAndFlush(Unpooled. EMPTY_BUFFER )

.addListener(ChannelFutureListener. CLOSE );

}

@Override

public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {

cause.printStackTrace(); //5

ctx.close();

}

服务器启动

package test01;

import io.netty.bootstrap.ServerBootstrap;

import io.netty.channel.*;

import io.netty.channel.nio.NioEventLoopGroup;

import io.netty.channel.socket.SocketChannel;

import io.netty.channel.socket.nio.NioServerSocketChannel;

import java.net.InetSocketAddress;

import java.util.concurrent.TimeUnit;

/**

* Created by wujiazhen on 2018/1/15.

public class EchoServer {

private int port ;

public EchoServer(){};

public EchoServer( int port){

this . port =port;

}

public static void main(String args[]){

new EchoServer( 2000 ).start();

}

public void start() {

NioEventLoopGroup group = new NioEventLoopGroup();

try {

1.创建 EventLoopGroup

2.创建 ServerBootstrap

3.指定使用 NIO 的传输 Channel

4.设置 socket 地址使用所选的端口

5.添加 EchoServerHandler 到 Channel 的 ChannelPipeline

ServerBootstrap bootstrap = new ServerBootstrap()

.channel(NioServerSocketChannel. class )

.group(group)

.localAddress( new InetSocketAddress( this .getPort()))

.childHandler( new ChannelInitializer<SocketChannel>() {

public void initChannel(SocketChannel socketChannel) throws Exception {

ChannelInitializer 。当一个新的连接被接受，一个新的子 Channel 将被创建，

ChannelInitializer 会添加我们EchoServerHandler 的实例到 Channel 的 ChannelPipeline。

正如我们如前所述，如果有入站信息，这个处理器将被通知。

socketChannel.pipeline().addLast( new EchoServerChannelHandler());

}

});

// 6.绑定的服务器;sync 等待服务器关闭

ChannelFuture future = bootstrap.bind().sync();

System. out .println(EchoServer. class .getName() + " started and listen on " + future.channel().localAddress());

//7.关闭 channel 和块，直到它被关闭

future.channel().closeFuture().sync();

} catch (InterruptedException e) {

e.printStackTrace();

} finally {

try {

group.shutdownGracefully().sync();

} catch (InterruptedException e) {

e.printStackTrace();

}

public int getPort() {

return port ;

}

public void setPort( int port) {

this . port = port;

}

客户端handler

package test01;

import io.netty.buffer.ByteBuf;

import io.netty.buffer.Unpooled;

import io.netty.channel.ChannelHandlerContext;

import io.netty.channel.SimpleChannelInboundHandler;

import io.netty.util.CharsetUtil;

/**

* Created by wujiazhen on 2018/1/15.

public class EchoClientChannelHandler extends SimpleChannelInboundHandler {

protected void channelRead0(ChannelHandlerContext channelHandlerContext, Object msg) throws Exception {

ByteBuf in = (ByteBuf)msg;

System. out .println( "client receive:" +in.toString(CharsetUtil. UTF_8 ));

}

@Override

public void channelActive(ChannelHandlerContext ctx) throws Exception {

System. out .println( "connect success" );

ctx.writeAndFlush(Unpooled. copiedBuffer ( "客户端：建立....." ,CharsetUtil. UTF_8 ));

super .channelActive(ctx);

}

客户端启动

package test01;

import io.netty.bootstrap.Bootstrap;

import io.netty.channel.ChannelFuture;

import io.netty.channel.ChannelInitializer;

import io.netty.channel.nio.NioEventLoopGroup;

import io.netty.channel.socket.SocketChannel;

import io.netty.channel.socket.nio.NioServerSocketChannel;

import io.netty.channel.socket.nio.NioSocketChannel;

/**

* Created by wujiazhen on 2018/1/15.

public class EchoClient {

public static void main(String[] args){

new EchoClient().start();

}

public void start(){

NioEventLoopGroup group = new NioEventLoopGroup();

try {

Bootstrap bootstrap = new Bootstrap();

bootstrap.group(group)

//区别与服务端的channel,客户端用NioSocketChannel

.channel(NioSocketChannel. class )

.remoteAddress( "127.0.0.1" , 2000 )

.handler( new ChannelInitializer<SocketChannel>() {

protected void initChannel(SocketChannel socketChannel) throws Exception {

socketChannel.pipeline().addLast( new EchoClientChannelHandler ());

}

});

ChannelFuture sync = bootstrap.connect().sync();

sync.channel().closeFuture().sync();

} catch (InterruptedException e) {

e.printStackTrace();

} finally {

try {

group.shutdownGracefully().sync();

} catch (InterruptedException e) {

e.printStackTrace();

}

一、netty初学，简单的echo服务器，客户端

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