【Java】Netty创建网络服务端客户端（TCP/UDP）

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这篇文章主要介绍Netty创建网络服务端客户端示例。
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文章目录

• • :smirk:1. Netty介绍
  • :blush:2. 环境安装与配置
  • :satisfied:3. TCP应用示例
  • :satisfied:4. UDP应用示例

😏1. Netty介绍

Netty官网：https://netty.io/

Netty是一个基于Java的异步事件驱动的网络应用程序框架，专门用于快速开发高性能、可扩展和可维护的网络服务器和客户端。它提供了简单而强大的API，使开发人员能够轻松地构建各种网络应用，包括TCP、UDP、HTTP、WebSocket等。

以下是一些关键特点和功能：

1.异步和事件驱动：Netty使用非阻塞I/O模型，通过异步事件驱动方式处理网络操作，提供了卓越的性能和可扩展性。

2.高性能：Netty通过有效地利用底层操作系统提供的机制（如选择器、零拷贝等）来实现高效的数据传输和处理，以满足对性能和吞吐量的要求。

3.安全：Netty提供了强大的加密和认证支持，包括SSL/TLS和各种认证机制，保护网络通信的安全性。

4.多协议支持：Netty支持多种主流的网络协议，如TCP、UDP、HTTP、WebSocket等，使开发人员可以方便地构建不同类型的网络应用。

5.灵活的处理程序模型：Netty采用了高度可扩展的处理程序（Handler）模型，使开发人员可以按需配置和组合处理程序来处理网络事件和数据，实现复杂的业务逻辑。

6.内置编解码器：Netty提供了丰富的内置编解码器，使开发人员能够轻松地处理各种协议和数据格式，简化了网络通信中的数据编解码工作。

7.完善的文档和社区支持：Netty拥有完善的官方文档、示例代码和教程，以及活跃的社区支持，使开发人员能够快速上手并解决问题。

😊2. 环境安装与配置

IDEA创建Netty工程，只要在pom.xml中引入如下依赖：

    <dependencies>         <dependency>             <groupId>io.netty</groupId>             <artifactId>netty-all</artifactId>             <version>4.1.49.Final</version>         </dependency>     </dependencies> 

😆3. TCP应用示例

创建TCP服务端客户端，需要先开启通道Channel，然后再有一个事件处理Handler，下面就创建这4个类：

NettyServer.java

package org.example;  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.NioEventLoopGroup; import io.netty.channel.socket.SocketChannel; import io.netty.channel.socket.nio.NioServerSocketChannel; import io.netty.handler.logging.LogLevel; import io.netty.handler.logging.LoggingHandler;  public class NettyServer {     private final int port;      public NettyServer(int port) {         this.port = port; // server port     }      public void start() 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, 128)                     .handler(new LoggingHandler(LogLevel.INFO))                     .childHandler(new ChannelInitializer<SocketChannel>() {                         @Override                         public void initChannel(SocketChannel ch) throws Exception {                             ch.pipeline().addLast(new NettyServerHandler()); // channel to handler                         }                     });              ChannelFuture f = b.bind(port).sync();             System.out.println("Server started on port " + port);              f.channel().closeFuture().sync();         } finally {             workerGroup.shutdownGracefully();             bossGroup.shutdownGracefully();         }     }      public static void main(String[] args) throws Exception {         int port = 8080;         NettyServer server = new NettyServer(port);         server.start();     } } 

NettyServerHandler.java

package org.example;  import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.*; import io.netty.util.CharsetUtil;  public class NettyServerHandler extends ChannelInboundHandlerAdapter {     /**      * 读取数据实际(这里我们可以读取客户端发送的消息)      * @param ctx 上下文对象      * @param msg 客户端发送的数据      * @throws Exception      */     @Override     public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {         System.out.println("server ctx =" + ctx);         Channel channel = ctx.channel();         // 将 msg 转成一个 ByteBuf         // ByteBuf 是 Netty 提供的，不是 NIO 的 ByteBuffer.         ByteBuf buf = (ByteBuf) msg;         System.out.println("客户端发送的消息是: " + buf.toString(CharsetUtil.UTF_8));         System.out.println("客户端地址: " + channel.remoteAddress());     }      /**      * 读取完毕，回复      * @param ctx      * @throws Exception      */     @Override     public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {         // writeAndFlush 是 write + flush 将数据写入到缓存，并刷新         ctx.writeAndFlush(Unpooled.copiedBuffer("Hello, Client!", CharsetUtil.UTF_8));     }      /**      * 处理异常, 一般是需要关闭通道      * @param ctx      * @param cause      * @throws Exception      */     @Override     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {         ctx.close();     } } 

NettyClient.java

package org.example;  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 NettyClient {     private final String host;     private final int port;      public NettyClient(String host, int port) {         this.host = host; // ip         this.port = port; // port     }      public void start() throws Exception {         EventLoopGroup group = new NioEventLoopGroup();          try {             Bootstrap b = new Bootstrap();             b.group(group)                     .channel(NioSocketChannel.class)                     .option(ChannelOption.TCP_NODELAY, true)                     .handler(new ChannelInitializer<SocketChannel>() {                         @Override                         public void initChannel(SocketChannel ch) throws Exception {                             ch.pipeline().addLast(new NettyClientHandler());                         }                     });              ChannelFuture f = b.connect(host, port).sync();             System.out.println("Connected to " + host + ":" + port);              f.channel().closeFuture().sync();         } finally {             group.shutdownGracefully();         }     }      public static void main(String[] args) throws Exception {         String host = "localhost";         int port = 8080;         NettyClient client = new NettyClient(host, port);         client.start();     } } 

NettyClientHandler.java

package org.example;  import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.ChannelInboundHandlerAdapter; import io.netty.util.CharsetUtil;  public class NettyClientHandler extends ChannelInboundHandlerAdapter {     /**      * 通道创建就绪后触发      * @param ctx      * @throws Exception      */     @Override     public void channelActive(ChannelHandlerContext ctx) throws Exception {         System.out.println("client ctx =" + ctx);         ctx.writeAndFlush(Unpooled.copiedBuffer("Hello, Server!", CharsetUtil.UTF_8));     }      /**      * 当通道有读取事件时，会触发      * @param ctx      * @param msg      * @throws Exception      */     @Override     public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {         ByteBuf buf = (ByteBuf) msg;         System.out.println("服务器回复的消息:" + buf.toString(CharsetUtil.UTF_8));         System.out.println("服务器的地址： "+ ctx.channel().remoteAddress());     }      /**      * 处理异常, 一般是需要关闭通道      * @param ctx      * @param cause      * @throws Exception      */     @Override     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {         cause.printStackTrace();         ctx.close();     } } 

分别运行服务端和客户端类，结果如下：

😆4. UDP应用示例

跟上面TCP类似，UDP也是要创建Channel和Handler，下面创建这4个类：

UDPServer.java

package org.example;  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.DatagramChannel; import io.netty.channel.socket.nio.NioDatagramChannel;  public class UDPServer {     private final int port;      public UDPServer(int port) {         this.port = port;     }      public void start() throws Exception {         EventLoopGroup group = new NioEventLoopGroup();          try {             Bootstrap b = new Bootstrap();             b.group(group)                     .channel(NioDatagramChannel.class)                     .handler(new ChannelInitializer<DatagramChannel>() {                         @Override                         protected void initChannel(DatagramChannel ch) throws Exception {                             ch.pipeline().addLast(new UDPServerHandler());                         }                     });              ChannelFuture f = b.bind(port).sync();             System.out.println("Server started on port " + port);             f.channel().closeFuture().sync();         } finally {             group.shutdownGracefully();         }     }      public static void main(String[] args) throws Exception {         int port = 8888;         UDPServer server = new UDPServer(port);         server.start();     } } 

UDPServerHandler.java

package org.example;  import io.netty.buffer.Unpooled; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.SimpleChannelInboundHandler; import io.netty.channel.socket.DatagramPacket; import io.netty.util.CharsetUtil;  public class UDPServerHandler extends SimpleChannelInboundHandler<DatagramPacket> {     @Override     protected void channelRead0(ChannelHandlerContext ctx, DatagramPacket msg) throws Exception {         // 处理接收到的数据         String receivedMessage = msg.content().toString(CharsetUtil.UTF_8);         System.out.println("Received message: " + receivedMessage);          // 响应客户端         String responseMessage = "Hello, client!";         DatagramPacket responsePacket = new DatagramPacket(Unpooled.copiedBuffer(responseMessage, CharsetUtil.UTF_8),                 msg.sender());         ctx.writeAndFlush(responsePacket);     } } 

UDPClient.java

package org.example;  import io.netty.bootstrap.Bootstrap; import io.netty.buffer.Unpooled; 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.DatagramChannel; import io.netty.channel.socket.DatagramPacket; import io.netty.channel.socket.nio.NioDatagramChannel; import io.netty.util.CharsetUtil;  import java.net.InetSocketAddress;  public class UDPClient {     private final String host;     private final int port;      public UDPClient(String host, int port) {         this.host = host;         this.port = port;     }      public void start() throws Exception {         EventLoopGroup group = new NioEventLoopGroup();          try {             Bootstrap b = new Bootstrap();             b.group(group)                     .channel(NioDatagramChannel.class)                     .handler(new ChannelInitializer<DatagramChannel>() {                         @Override                         protected void initChannel(DatagramChannel ch) throws Exception {                             ch.pipeline().addLast(new UDPClientHandler());                         }                     });              ChannelFuture f = b.bind(0).sync();             System.out.println("Client started");              // 发送消息给服务端             String message = "Hello, server!";             DatagramPacket packet = new DatagramPacket(Unpooled.copiedBuffer(message, CharsetUtil.UTF_8),                     new InetSocketAddress(host, port));             f.channel().writeAndFlush(packet).sync();              f.channel().closeFuture().sync();         } finally {             group.shutdownGracefully();         }     }      public static void main(String[] args) throws Exception {         String host = "localhost";         int port = 8888;         UDPClient client = new UDPClient(host, port);         client.start();     } } 

UDPClientHandler.java

package org.example;  import io.netty.channel.ChannelHandlerContext; import io.netty.channel.SimpleChannelInboundHandler; import io.netty.channel.socket.DatagramPacket; import io.netty.util.CharsetUtil;  public class UDPClientHandler extends SimpleChannelInboundHandler<DatagramPacket> {     @Override     protected void channelRead0(ChannelHandlerContext ctx, DatagramPacket msg) throws Exception {         // 处理接收到的数据         String receivedMessage = msg.content().toString(CharsetUtil.UTF_8);         System.out.println("Received response from server: " + receivedMessage);     } } 

运行结果如下：

以上。