netty编程之UDP

写在前面

源码。
UDP，user datagram protocol,是internet协议簇中无连接的传输协议，因为无连接所以相比于TCP需要维护更少的信息以及网络交互，所以具有更高的效率。本文看下netty是如何实现的，和TCP方式差别不大，下面具体代码实现过程中看下哪里不同。虽然小有不同，但套路相同。

1：代码实现

1.1：server

server main：

package com.dahuyou.netty.udp.server;import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioDatagramChannel;public class NettyServer {public static void main(String[] args) throws InterruptedException {EventLoopGroup group = new NioEventLoopGroup();try {Bootstrap b = new Bootstrap();b.group(group).channel(NioDatagramChannel.class).option(ChannelOption.SO_BROADCAST, true)    //广播.option(ChannelOption.SO_RCVBUF, 2048 * 1024)// 设置UDP读缓冲区为2M.option(ChannelOption.SO_SNDBUF, 1024 * 1024)// 设置UDP写缓冲区为1M.handler(new MyChannelInitializer());ChannelFuture f = b.bind(7397).sync();System.out.println("udp server start done.");f.channel().closeFuture().sync();} finally {//优雅的关闭释放内存group.shutdownGracefully();}}}

这里有个不同之处，使用的通道类是NioDatagramChannel,而TCP的是.channel(NioServerSocketChannel.class)。
MyChannelInitializer如下：

package com.dahuyou.netty.udp.server;import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioDatagramChannel;public class MyChannelInitializer extends ChannelInitializer<NioDatagramChannel> {private EventLoopGroup group = new NioEventLoopGroup();@Overrideprotected void initChannel(NioDatagramChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();// 解码转String，注意调整自己的编码格式GBK、UTF-8//pipeline.addLast("stringDecoder", new StringDecoder(Charset.forName("GBK")));pipeline.addLast(group, new MyServerHandler());}}

MyServerHandler:

package com.dahuyou.netty.udp.server;import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.socket.DatagramPacket;import java.nio.charset.Charset;
import java.text.SimpleDateFormat;
import java.util.Date;public class MyServerHandler extends SimpleChannelInboundHandler<DatagramPacket> {@Overrideprotected void channelRead0(ChannelHandlerContext ctx, DatagramPacket packet) throws Exception {String msg = packet.content().toString(Charset.forName("GBK"));System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()) + " UDP服务端接收到消息：" + msg);//向客户端发送消息String json = "通知：我已经收到你的消息\r\n";// 由于数据报的数据是以字符数组传的形式存储的，所以传转数据byte[] bytes = json.getBytes(Charset.forName("GBK"));DatagramPacket data = new DatagramPacket(Unpooled.copiedBuffer(bytes), packet.sender());ctx.writeAndFlush(data);//向客户端发送消息}}

这里有一个不同点，继承的是SimpleChannelInboundHandler，而TCP是ChannelInboundHandlerAdapter。

1.2：client

client main:

package com.dahuyou.netty.udp.client;import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.DatagramPacket;
import io.netty.channel.socket.nio.NioDatagramChannel;import java.net.InetSocketAddress;
import java.nio.charset.Charset;public class NettyClient {public static void main(String[] args) {EventLoopGroup group = new NioEventLoopGroup();try {Bootstrap b = new Bootstrap();b.group(group).channel(NioDatagramChannel.class).handler(new MyChannelInitializer());Channel ch = b.bind(7398).sync().channel();//向目标端口发送信息ch.writeAndFlush(new DatagramPacket(Unpooled.copiedBuffer("我是客户端小爱，你在吗！", Charset.forName("GBK")),new InetSocketAddress("127.0.0.1", 7397))).sync();ch.closeFuture().await();} catch (Exception e) {e.printStackTrace();} finally {group.shutdownGracefully();}}}

这里写数据需要使用DatagramPacket类进行封装，而TCP是直接写就行。同样channel类也不同。

MyChannelInitializer如下：

package com.dahuyou.netty.udp.client;import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.nio.NioDatagramChannel;public class MyChannelInitializer extends ChannelInitializer<NioDatagramChannel> {@Overrideprotected void initChannel(NioDatagramChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();// 解码转String，注意调整自己的编码格式GBK、UTF-8//pipeline.addLast("stringDecoder", new StringDecoder(Charset.forName("GBK")));pipeline.addLast(new MyClientHandler());}}

MyClientHandler如下：

package com.dahuyou.netty.udp.client;import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.socket.DatagramPacket;import java.nio.charset.Charset;
import java.text.SimpleDateFormat;
import java.util.Date;public class MyClientHandler extends SimpleChannelInboundHandler<DatagramPacket> {//接受服务端发送的内容@Overrideprotected void channelRead0(ChannelHandlerContext ctx, DatagramPacket packet) throws Exception {String msg = packet.content().toString(Charset.forName("GBK"));System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()) + " UDP客户端接收到消息：" + msg);}}