Java多播无法工作

我在业余时间写一个基于网络的小游戏，我需要一个服务器浏览器。我想通过Datagramsocket的多播来实现这一点

代码运行平稳，没有任何运行时或编译错误，但包未发送。我试着用线鲨嗅它。以下是我的发件人方法的代码：

public void sendRequest() throws UnknownHostException, InterruptedException{

    InetAddress adr = InetAddress.getByName(this.address); //Address = 239.0.0.4


    try(DatagramSocket serverSocket = new DatagramSocket()){

        for(int i = 0; i<10; i++){

            String msg = "request";

            DatagramPacket msgPacket = new DatagramPacket(
                    msg.getBytes(),
                    msg.getBytes().length,
                    adr,
                    this.port); //this.port == 8888


            serverSocket.send(msgPacket);


            Thread.sleep(150);


        }

        serverSocket.close();

    }
    catch(IOException ex){
        System.err.println("Error while trying to create DatagramSocket!");
        System.exit(1);
    }

}

public void sendRequest（）引发UnknownHostException、InterruptedException{
InetAddress adr=InetAddress.getByName（this.address）；//地址=239.0.0.4
try（datagramsocketserversocket=newdatagramsocket（））{
对于（int i=0；i