Netty udp给指定客户端发消息

udp server

package com.example.demo.udp;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.FixedRecvByteBufAllocator;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioDatagramChannel;

/**
 * A UDP server that responds to the QOTM (quote of the moment) request to a {@link UdpClient}.
 * 

 * Inspired by the official
 * Java tutorial.
 */
public final class UdpServer {

    private static final int PORT = Integer.parseInt(System.getProperty("port", "7686"));

    public static void main(String[] args) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group)