IPv6Test.java

import java.net.InetSocketAddress;
import java.nio.channels.SocketChannel;

public class IPv6Test {
    public static void main(String[] args) {
        // This is a well-known IPv6-only hostname provided by Google.
        String host = "ipv6.google.com";
        int port = 80; // Standard web port.

        System.out.println("Attempting to connect to " + host + " on port " + port + " using IPv6...");
        
        try {
            // Force the JVM to prefer IPv6 addresses.
            System.setProperty("java.net.preferIPv6Addresses", "true");
            
            SocketChannel socketChannel = SocketChannel.open();
            socketChannel.socket().connect(new InetSocketAddress(host, port), 5000); // 5-second timeout
            
            if (socketChannel.isConnected()) {
                System.out.println("\nSUCCESS!");
                System.out.println("Java was able to successfully make an IPv6 connection from this machine.");
                System.out.println("This proves the issue is likely not with the server's core network configuration.");
                socketChannel.close();
            }
        } catch (Exception e) {
            System.out.println("\nFAILURE!");
            System.out.println("Java was UNABLE to make an IPv6 connection from this machine.");
            System.out.println("This is the root cause of the problem. Lavalink's IP rotation cannot function.");
            System.out.println("Error details: " + e.getMessage());
        }
    }
}