SpangBang Proxy

To realize receiving and transmitting UDP packets in different threads for parallel work in Java, you can use the DatagramSocket class along with the Thread class to create separate threads for receiving and transmitting. Here's an example of a simple UDP server that handles receiving and transmitting in different threads:

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

public class ParallelUDPServer {
    private static final int PORT = 12345;

    public static void main(String[] args) throws IOException {
        // Create a DatagramSocket for receiving UDP packets
        DatagramSocket receiveSocket = new DatagramSocket(PORT);

        // Create a thread for receiving UDP packets
        Thread receiveThread = new Thread(() -> {
            byte[] receiveBuffer = new byte[1024];
            while (true) {
                DatagramPacket receivePacket = new DatagramPacket(receiveBuffer, receiveBuffer.length);
                try {
                    receiveSocket.receive(receivePacket);
                    processReceivePacket(receivePacket);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });

        // Create a thread for transmitting UDP packets
        Thread transmitThread = new Thread(() -> {
            while (true) {
                // Simulate sending UDP packets to a client
                sendUDPPacket("Hello from the server!", "127.0.0.1", 6789);
                try {
                    Thread.sleep(5000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });

        // Start the threads
        receiveThread.start();
        transmitThread.start();
    }

    private static void processReceivePacket(DatagramPacket packet) {
        byte[] data = packet.getData();
        int length = packet.getLength();
        InetAddress address = packet.getAddress();
        int port = packet.getPort();

        System.out.println("Received packet:");
        for (int i = 0; i < length; i++) {
            System.out.print(data[i] + " ");
        }
        System.out.println();
        System.out.println("From: " + address + ":" + port);
    }

    private static void sendUDPPacket(String message, String host, int port) throws IOException {
        byte[] sendData = message.getBytes();
        DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, InetAddress.getByName(host), port);
        DatagramSocket socket = new DatagramSocket();
        socket.send(sendPacket);
        socket.close();
    }
}

In this example, the ParallelUDPServer class creates two threads: one for receiving UDP packets (receiveThread) and another for transmitting UDP packets (transmitThread).

You can check it with the ping command from the command line in Windows. It is enough to enter it, with a space - the data of the proxy server (including the number of the port used) and press Enter. The reply message will tell you whether or not you have received a reply from the remote server. If not, the proxy is unavailable, respectively.

Technically, the ISP cannot block all VPN servers. But it is possible to block some of them. In this case, you can use any other VPN service. But you have to be careful with "free" ones, as they often make money from collecting and selling users' confidential data.

If you plan to use a proxy every day, it is recommended to pay attention to paid services. There, the connection is as reliable as possible, with no bandwidth limitations. However, the performance of numerous free proxies is not guaranteed.

SIP is a virtual telephony service. A proxy server in this case is used to collect traffic, its conversion and further transmission to the subscriber via cellular communication. It is mainly used by call centers to communicate with customers.