How can I scrape a udp BitTorrent tracker in Java?

Question

I send a scrape packet, seeders, downloaders and leechers always return as 0.

Here is my initial connection and scraper code.

public void scrape() {
        for (final String infohash : infoHashes) {
            hashes += infohash;
        }
        outStream.writeByte(hashes.getBytes());

}

For example my output is

3617635676834215396 0

Answer 1

for (final String infohash : infoHashes) {
    hashes += infohash;
}
outStream.writeByte(hashes.getBytes());

My guess is that you're using hex-encoded hashes. UDP scrapes expect them in their raw format.