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();
@Override
protected 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> {
@Override
protected 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> {
@Override
protected 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
@Override
protected 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);
}
}
启动server：
启动client：
