Android上的UDP打孔; UDP服务器

我正在尝试在Android上为我的udp服务器实现udp打孔.事情应该像这样:

客户端(在nat之后;可能是3G,...)向服务器发送DatagramPacket(服务器具有公共IP;端口也称为45555).客户端重复发送具有给定延迟的数据报

一旦服务器收到数据报,它就会每隔500毫秒发回一次数据报("信号").

如果打孔工作,客户应该接收这些信号

这是我当前的客户端实现(Android):

    //in onCreate()
    DatagramSocket socket = new DatagramSocket(46222);
    socket.setSoTimeout(2000);
    final Thread t = new Thread(new Runnable(){

        @Override
        public void run() {
            int delay = Integer.parseInt(e2.getText().toString());//e1 and e2 are EditTexts
            String ip = e1.getText().toString();
            try {
                DatagramPacket packet = new DatagramPacket(new byte[1],1, InetAddress.getByName(ip), 45555);
                while(!cleanUp){//cleanUp is set to true in onPause()
                    lock.lock(); //Lock lock = new ReentrantLock();
                    socket.send(packet);
                    lock.unlock();
                    Thread.sleep(delay);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }finally{
                if(socket!=null)
                    socket.close();
            }
        }

    });
    final Thread t2 = new Thread(new Runnable(){

        @Override
        public void run() {
            try {
                Thread.sleep(1000);
                DatagramPacket packet = new DatagramPacket(new byte[1],1);
                while(!cleanUp){
                    lock.lock();
                    try{
                        socket.receive(packet);
                    }catch(SocketTimeoutException e){
                        lock.unlock();
                        Thread.sleep(15);
                        continue;
                    }
                    lock.unlock();
                    final String s = tv.getText().toString()+"signal\n";
                    MainActivity.this.runOnUiThread(new Runnable(){

                        @Override
                        public void run() {
                            tv.setText(s);//tv is a TextView
                        }

                    });
                    Thread.sleep(10);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
            finally{
                if(socket!=null)
                    socket.close();
            }
        }

    });
    //start both threads

这是服务器端实现(Java):

//int static void main(String[] args):
final Thread t = new Thread(new Runnable(){

        @Override
        public void run() {
            try {
                DatagramPacket packet = new DatagramPacket(new byte[1],1, addr, port);
                DatagramSocket socket = new DatagramSocket();
                System.out.println("send");
                while(true){
                    socket.send(packet);
                    Thread.sleep(500);
                }
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

    });
    final Thread t2 = new Thread(new Runnable(){

        @Override
        public void run() {
            try {
                DatagramPacket packet = new DatagramPacket(new byte[1],1);
                DatagramSocket socket = new DatagramSocket(45555);
                socket.receive(packet);
                addr = packet.getAddress(); //private static field InetAddress addr
                port = packet.getPort();
                System.out.println(addr+":"+ packet.getPort()); //field int port
                t.start();
                while(true){
                    socket.receive(packet);
                    System.out.println("idle");
                }
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

    });
    t2.start();

当客户端和服务器位于同一个专用网络中时,一切正常.为了模仿公共服务器,我在我的计算机上运行服务器端代码,并在我的路由器上设置一个端口(具有公共IP)*.客户端将其数据包发送到路由器的公共IP.但在这两种情况下(我的智能手机通过我的wlan网络/ 3G或E连接到互联网)没有收到信号(服务器接收客户端的数据报)

那么为什么打孔过程不起作用呢？

问候

*:路由器会将发送到其端口45555的任何udp数据包转发到我的计算机