【Java】Netty创建网络服务端客户端（TCP/UDP）

😏★,°:.☆(￣▽￣)/$:.°★ 😏
这篇文章主要介绍Netty创建网络服务端客户端示例。
学其所用，用其所学。——梁启超
欢迎来到我的博客，一起学习，共同进步。
喜欢的朋友可以关注一下，下次更新不迷路🥞

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：

io.nettynetty-all4.1.49.Final 😆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() { @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() { @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() { @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 { @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() { @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 { @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。