你上面的netty4.x的代码，里面没有体现发送的组播地址和端口，请补充完整

好的，以下是补充完整后的netty4.x代码：

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelOption;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.DatagramPacket;
import io.netty.channel.socket.nio.NioDatagramChannel;
import java.net.InetSocketAddress;

public class MulticastSender {
    
    private static final String MULTICAST_IP = "224.0.0.1";
    private static final int PORT = 8888;
    
    public static void main(String[] args) throws Exception {
        Bootstrap b = new Bootstrap();
        NioEventLoopGroup group = new NioEventLoopGroup();
        try {
            b.group(group)
             .channel(NioDatagramChannel.class)
             .option(ChannelOption.SO_BROADCAST, true)
             .handler(new SimpleChannelInboundHandler<DatagramPacket>() {
                @Override
                public void channelActive(ChannelHandlerContext ctx) throws Exception {
                    String msg = "Hello, World!";
                    ByteBuf buf = Unpooled.copiedBuffer(msg.getBytes());
                    InetSocketAddress multicastAddress = new InetSocketAddress(MULTICAST_IP, PORT);
                    DatagramPacket packet = new DatagramPacket(buf, multicastAddress);
                    ctx.writeAndFlush(packet);
                }
                
                @Override
                protected void channelRead0(ChannelHandlerContext ctx, DatagramPacket packet) throws Exception {
                    // Do nothing, just send packet
                }
            });
            
            ChannelFuture f = b.bind(0).sync();
            f.channel().closeFuture().await();
        } finally {
            group.shutdownGracefully();
        }
    }
}

在这个代码中，我们通过 `InetSocketAddress` 来指定了组播地址和端口。具体来说，`224.0.0.1` 是 IPv4 中的标准组播地址，表示所有与本地网络相连的主机都可以接收到这个消息。而 `8888` 是我们指定的端口号，用于标识该组播消息。这样，在发送消息时，我们就可以将消息打包成 `DatagramPacket`，并指定目标地址为 `InetSocketAddress`，从而将消息发送到指定的组播地址和端口。