src/main/java/tracker/DataCaptureProxy.java

package tracker;

import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import org.simpleframework.http.Request;
import org.simpleframework.http.Response;
import org.simpleframework.http.core.Container;

/**
 * 拦截 announce 请求，打印参数后转发给真实 Tracker。
 */
public class DataCaptureProxy implements Container {

    private final String trackerHost;
    private final int    trackerPort;

    public DataCaptureProxy(String trackerHost, int trackerPort) {
        this.trackerHost = trackerHost;
        this.trackerPort = trackerPort;
    }

    @Override
    public void handle(Request req, Response resp) {
        try {
            // 提取并打印关键参数
            String infoHash  = req.getParameter("info_hash");
            String uploaded  = req.getParameter("uploaded");
            String downloaded= req.getParameter("downloaded");
            String passkey   = req.getParameter("passkey");
            System.out.println(
                "Captured announce → info_hash=" + infoHash +
                ", uploaded=" + uploaded +
                ", downloaded=" + downloaded +
                ", passkey=" + passkey
            );

            // 构造转发 URL
            String path  = req.getPath().getPath();
            String query = req.getQuery().toString();
            String targetUrl = "http://" + trackerHost + ":" + trackerPort
                             + path + "?" + query;

            HttpURLConnection connection =
                (HttpURLConnection) new URL(targetUrl).openConnection();
            connection.setRequestMethod("GET");

            // 转发响应码和类型
            resp.setCode(connection.getResponseCode());
            String ct = connection.getContentType();
            if (ct != null) resp.setValue("Content-Type", ct);

            // 转发响应体
            try (InputStream in = connection.getInputStream();
                 OutputStream out = resp.getOutputStream()) {
                byte[] buf = new byte[8192];
                int  len;
                while ((len = in.read(buf)) != -1) {
                    out.write(buf, 0, len);
                }
            }

        } catch (Exception e) {
            try {
                resp.setCode(500);
                resp.close();
            } catch (Exception ignore) {}
            e.printStackTrace();
        }
    }
}