Netty multicast demo.

gistfile1.java

package me.filippov.netty_demo;

import io.netty.bootstrap.Bootstrap;
import io.netty.bootstrap.ChannelFactory;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.DatagramPacket;
import io.netty.channel.socket.InternetProtocolFamily;
import io.netty.channel.socket.nio.NioDatagramChannel;

import java.net.*;
import java.util.Enumeration;

public class MulticastServer extends Thread {
    private InetSocketAddress groupAddress;

    public MulticastServer(InetSocketAddress groupAddress) {
        this.groupAddress = groupAddress;
    }

    private class MulticastHandler extends  SimpleChannelInboundHandler<DatagramPacket> {
         @Override
        protected void channelRead0(ChannelHandlerContext ctx, DatagramPacket msg) throws Exception {
            System.out.println("receive");
        }
    }

    public void run() {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            NetworkInterface ni = NetworkInterface.getByName("en1");
            Enumeration<InetAddress> addresses = ni.getInetAddresses();
            InetAddress localAddress = null;
            while (addresses.hasMoreElements()) {
                InetAddress address = addresses.nextElement();
                if (address instanceof Inet4Address){
                    localAddress = address;
                }
            }

            Bootstrap b = new Bootstrap()
                .group(group)
                .channelFactory(new ChannelFactory<NioDatagramChannel>() {
                    @Override
                    public NioDatagramChannel newChannel() {
                        return new NioDatagramChannel(InternetProtocolFamily.IPv4);
                    }
                })
                .localAddress(localAddress, groupAddress.getPort())
                .option(ChannelOption.IP_MULTICAST_IF, ni)
                .option(ChannelOption.SO_REUSEADDR, true)
                .handler(new ChannelInitializer<NioDatagramChannel>() {
                    @Override
                    public void initChannel(NioDatagramChannel ch) throws Exception {
                        ch.pipeline().addLast(new MulticastHandler());
                    }
                });

            NioDatagramChannel ch = (NioDatagramChannel)b.bind(groupAddress.getPort()).sync().channel();
            ch.joinGroup(groupAddress, ni).sync();
            ch.closeFuture().await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (SocketException e) {
            e.printStackTrace();
        } finally {
            group.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        InetSocketAddress groupAddress = new InetSocketAddress("239.255.27.1", 1234);
        new MulticastServer(groupAddress).run();
    }
}