使用DatagramSocket的Java UDP STUN打孔

我试图通过NAT向客户端发送udp数据包，我们都属于不同的NAT，我们熟悉STUN的理论，因此实现这一目标的方法是“打孔”我们的方式通过一个简单的STUN服务器..

基本上，服务器只返回“连接”的另一个客户端的外部IP地址和端口，然后我可以使用它通过NAT将数据包发送到客户端...但是我们设法获得了彼此的外部IP和端口 . 发送后我们仍然无法收到任何东西......经过论坛搜索和数小时的头部刮伤后，我们仍然无法找到解决方案...想知道是否有人熟悉STUN能够给我们一些关于我们哪里出错的指示或建议......

以下是我们写的小客户......

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.net.SocketException;
import java.net.UnknownHostException;

import javax.swing.JOptionPane;


public class Client {

DatagramSocket socket;

public Client(){
    try {
        socket = new DatagramSocket();
        String data = "Initiate Stun Server";
        byte[] receive = data.getBytes();

        InetAddress host = InetAddress.getByName("the.stun.server.ipaddress");
        DatagramPacket pk = new DatagramPacket(receive,receive.length,host,9345);
        socket.send(pk); //send packet to server to initiate udp communication

        //spawn a new Thread to listen for any incoming packets
        new Thread(){
            public void run(){
                byte[] r;
                DatagramPacket rp;
                while(true){
                    System.out.println("Start listening on new socket");
                    r = new byte[1024];
                    rp = new DatagramPacket(r,r.length);
                    try {
                        socket.receive(rp);
                        System.out.println(new String(rp.getData()));
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }.start();

        String m = JOptionPane.showInputDialog(null,"Enter message to send");
        InetAddress connect = InetAddress.getByName(JOptionPane.showInputDialog(null,"Enter address to send message to"));//This is where we input the external ip
        int connectPort = Integer.parseInt(JOptionPane.showInputDialog(null,"Enter port of the addressee"));//input port
        DatagramPacket p = new DatagramPacket(m.getBytes(),m.getBytes().length,connect,connectPort);
        socket.send(p);

    } catch (SocketException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (UnknownHostException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

public static void main(String args[]){
    Client c = new Client();
}

}