组播服务器接收发送的相同数据

Question

我正在尝试允许连接到UDP服务器的客户端将数据包发送到服务器，我正在运行服务器，以便可以将数据包发送到客户端，但是尝试通过客户端将数据包发送回服务器似乎会创建一些奇怪的错误。

如果我启动服务器，然后打开一个客户端，则客户端将接收到来自服务器的第一个数据包，然后客户端尝试将数据包发送到服务器，这是服务器接收到的，但是随后客户端抛出此错误

Exception in thread "main" java.lang.NumberFormatException: For input string: "testing"
    at sun.misc.FloatingDecimal.readJavaFormatString(Unknown Source)
    at java.lang.Double.parseDouble(Unknown Source)
    at Pong.PongUDPClient.main(PongUDPClient.java:71)

第71行将在代码中指向服务器控制台只是打印出应发送给客户端的数据，

这是服务器的完整代码

package Pong;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.MulticastSocket;
import java.net.Socket;

//This is the actual server
public class PongUDPServerThread extends Thread {

//speed to send data
private long dataSpeed = 10;
private int port = 4447;
private int idPlayer = 0;
private PongModel model;
private PongView  view;
private PongPlayerThread players[] = new PongPlayerThread[2];
private MulticastSocket socket = null;
private InetAddress group;
private DatagramPacket packet = null;
private int ID = 1;

public PongUDPServerThread() throws IOException 
{
    super("PongUDPServerThread");
}

public String rtnInfo()
{
    String str;
    str = model.getBall().getX() + ":" +
          model.getBall().getY() + ":" +
          model.getBats()[0].getX() + ":" +
          model.getBats()[0].getY() + ":" +
          model.getBats()[1].getX() + ":" +
          model.getBats()[1].getY();
    return str;
}

public void setupPong() throws IOException 
{
    System.out.println("Pong");
    model = new PongModel();
    view  = new PongView();
            new PongController( model, view );

    model.addObserver( view );       // Add observer to the model

    //view.setVisible(true);           // Display Screen
    model.makeActiveObject();        // Start play
    //start server
    socket = new MulticastSocket(port);
    InetAddress group = InetAddress.getByName("230.0.0.1");
    socket.setReuseAddress(true);
    socket.joinGroup(group);
    //socket.setReuseAddress(true);
    //Inform server user
    System.out.println("Server is running");
}

public void run()
{
    //Server loop
    while(true)
    {

        //Receive the data
        try
        {
        byte[] receiveBuf = new byte[256];
        packet = new DatagramPacket(receiveBuf, receiveBuf.length);
        socket.receive(packet);

        String received = new String(packet.getData(), 0, packet.getLength());

        System.out.println(received);
        }
        catch (IOException e)
        {

        }


        try
        {
            byte[] buf = new byte[256];

            //Gather data
            buf = rtnInfo().getBytes();
            //System.out.println(buf.toString());

            //Send data
            packet = new DatagramPacket(buf, buf.length, InetAddress.getByName("230.0.0.1"), port);
            socket.send(packet);

            //Sleep the server
            try
            {
                sleep((long)dataSpeed);
            }
            catch (InterruptedException e)
            {

            }
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
    }

    //socket.close();

}

}

这是客户代码

package Pong;

import java.io.*;
import java.net.*;
import java.util.*;

public class PongUDPClient {

private static int port = 4447;

public static void main(String[] args) throws IOException
{

    //Setup pong rdy
    PongModel model = new PongModel();
    PongView  view  = new PongView();
                      new PongController( model, view );

    model.addObserver( view );       // Add observer to the model

    String pos;

    model.makeActiveObject();        // Start play
    //model.clientModel();

    MulticastSocket socket = new MulticastSocket(port);
    //socket.setReuseAddress(true);
    InetAddress address = InetAddress.getByName("230.0.0.1");
    //Join the UDP list port
    socket.setReuseAddress(true);
    socket.joinGroup(address);

    DatagramPacket packet;
    view.setVisible(true);           // Display Screen

    System.out.println("Connected");
    //Id is sent here.

    while(true)
    {

        //Send data to server
        try
        {
            byte[] receiveBuf = new byte[256];

            //Gather data
            receiveBuf = "testing".getBytes();
            //System.out.println(buf.toString());

            //Send data
            packet = new DatagramPacket(receiveBuf, receiveBuf.length, InetAddress.getByName("230.0.0.1"), port);
            socket.send(packet);

            //Sleep the server
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }

        byte[] buf = new byte[256];
        packet = new DatagramPacket(buf, buf.length);
        socket.receive(packet);

        String  received = new String(packet.getData(), 0, packet.getLength());
        //System.out.println("Server data: " + received);

        String[] posValues = received.split(":");

        model.getBall().setX(Double.parseDouble(posValues[0])); // <-- Line 71
        model.getBall().setY(Double.parseDouble(posValues[1]));
        model.getBats()[0].setX(Double.parseDouble(posValues[2]));
        model.getBats()[0].setY(Double.parseDouble(posValues[3]));
        model.getBats()[1].setX(Double.parseDouble(posValues[4]));
        model.getBats()[1].setY(Double.parseDouble(posValues[5]));

        //Check for keyboard input

        if(PongController.moveUp == true && PongController.moveDown == false)
        {
            System.out.println("Up");
            PongController.moveUp = false;
        }
        else if(PongController.moveUp == false && PongController.moveDown == true)
        {
            System.out.println("Down");
            PongController.moveDown = false;
        }
        else
        {
            //serverOut.println("nothing");
        }


    }
}

}

停留了一段时间，似乎找不到如何使用多播将数据包从客户端发送到服务器的任何教程。

Answer 1

您正在经历多播回送。 使用MulticastSocket#setLoopbackMode(true)将其关闭，或者，如果该对等方只是发送MulticastSocket#setLoopbackMode(true)播组而不接收，则完全不需要加入该组。