Java-Client PHP-Server UDP Hole Punching example code

Question

I\'m working on a project that will require ea p2p server, but I haven\'t found any java-client php-server example code. I understand the concept of how udp hole punching works

Answer 1

I was facing a similar problem. And was trying to solve it in a similar way.

Some parts of your code look wrong to me. Sockets in Java are made for TCP but the title says UDP. Therefore u should use DatagramSockets. But then we come to the point where i stuck too. HTTP-Requests use tcp as well, so opening the port with HTTP might lead to a corrupt port, after tcp session was closed. (Just a guess)

---

public class Main {

    public static void main(String[] args) {

        try
        {

            String httpRequest = "GET /index.php HTTP/1.1\n" +
                    "Host: <PHP SERVER NAME HERE>";

            InetAddress IPAddress = InetAddress.getByName(<PHP SERVER IP HERE>);

            DatagramSocket clientSocket = new DatagramSocket();
            byte[] sendData = new byte[1024];
            byte[] receiveData = new byte[1024];
            String sentence = httpRequest;
            sendData = sentence.getBytes();

            DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 80);
            clientSocket.send(sendPacket);
            DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
            clientSocket.receive(receivePacket);

            String modifiedSentence = new String(receivePacket.getData());
            System.out.println("FROM SERVER:" + modifiedSentence);

            clientSocket.close();

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

    }


}

The Code above theoretically sents a HTTP over UDP request. So that the displayed Port will be the UDP one. In my case i didnt get any response from the PHP Server and stuck at clientSocket.recieve(..) . I guess because the firewall of my webserver is blocking udp packets. If the code works by anyone i would proceed like this:

1. save all accessing ips and ports to a DB and list them to the other client.
2. Write ur Data in DatagramPackets like above to the other client.

I hope this may help. If anyone can get it completly working i would also be interested in it :)