Turn&#39;s [TTorrent][1] is a pure Java bit torrent library.


  [1]: http://mpetazzoni.github.io/ttorrent/

[Snark][1] by Three Rings is a very lightweight bitorrent library that will give you basic torrent features.

Was [originally][2] written by Mark Wielaard. A github source can be found here https://github.com/akerigan/born-again-snark

[1]:http://www.staging.threerings.net/snark.html
[2]:http://www.klomp.org/snark/



I have created a [Bitlet Fork](https://github.com/Toilal/bitlet) on Github.

It&#39;s LGPLed, and it&#39;s running faster than ttorent. 



[Azureus][1] (now named [Vuze][2]) gives you a plugin API. Using this API you can plug your code into Azureus. Start it inside your program, and listen/respond to its events.


  [1]: http://sourceforge.net/projects/azureus/
  [2]: https://en.wikipedia.org/wiki/Vuze

Azureus is written in Java - is most likely not &quot;simple&quot; but quite likely &quot;decent&quot; :)

Adding to answer from jjnguy  : The code seems to be at http://code.google.com/p/snark/ and not in the repo pointed to in the link you&#39;ve provided.

I&#39;ve not used it, but a Google search showed up [YAIRCC](http://sourceforge.net/projects/yaircc/). Describes itself as &quot;A lightweight Java Bittorrent library and client&quot;.

Transdroid and Transdroid-desktop are libraries for adroid, that can also be used in java to control existing torrent clients.

I need to deserialize some JavaScript object represented in JSON to an appropriate C# class. Given the nice features of automatic properties, I would prefer having them in these classes as opposed to just having fields. Unfortunately, the .NET serialization engine (at least, by default) totally ignores automatic properties on deserialization and only cares about the backing field, which is obviously not present in the JavaScript object.

Given that there&#39;s [no standard way to name backing fields][1] and to be honest I don&#39;t even want to bother with the &quot;let&#39;s create a JavaScript object that looks like it had C# backing fields&quot; approach as it sounds a bit dirty, the only way I could serialize JavaScript fields to C# auto-properties if I could force the serialization engine to somehow ignore the backing field and use the property directly. Unfortunately, I can&#39;t figure out how this is done or if this can be done at all. Any ideas would be appreciated.

**EDIT**: Here&#39;s an example:

Javascript:

    function Cat()
    {
        this.Name = &quot;Whiskers&quot;;
        this.Breed = &quot;Tabby&quot;;
    }
    var cat = new Cat();

This is then serialized to &quot;{Name: &#39;Whiskers&#39;}&quot;.

The C# class:

    [Serializable()]
    public class Cat
    {
        public string Name { get; set; }
        public string Breed { get; set; }
    }

And the deserialization code, that fails:

    new DataContractJsonSerializer(typeof(Cat)).ReadObject(inputStream);

And it is apparent from the exception that it fails because it is looking for the backing field.

**EDIT2**: Here&#39;s the exception, if that helps (no inner exceptions):

&gt; System.Runtime.Serialization.SerializationException
&gt;
&gt; &quot;The data contract type &#39;Test.Cat&#39;
&gt; cannot be deserialized because the
&gt; required data members
&gt; &#39;`&lt;Name&gt;k__BackingField, &lt;Breed&gt;k__BackingField`&#39; were not
&gt; found.&quot;

  [1]: https://stackoverflow.com/questions/371398/problems-with-auto-properties


C# automatic property deserialization of JSON

&gt;Related: [how-do-i-use-webrequest-to-access-an-ssl-encrypted-site-using-https][1]

How to send an HTTPS GET Request in C#?


  [1]: https://stackoverflow.com/questions/560804/how-do-i-use-webrequest-to-access-an-ssl-encrypted-site-using-https



How to send an HTTPS GET Request in C#

Are there any decent BitTorrent libraries for Java?  I need to program a simple torrent client, but it would be great if I didn&#39;t have to write everything from scratch.

Java BitTorrent library

<p>Are there any decent BitTorrent libraries for Java?  I need to program a simple torrent client, but it would be great if I didn't have to write everything from scratch.</p>


I am thinking of creating a debug tool for my Java application.

I am wondering if it is possible to get a stack trace, just like ``Exception.printStackTrace()`` but without actually throwing an exception?

My goal is to, in any given method, dump a stack to see who the method caller is.

Is there a way to dump a stack trace without throwing an exception in java?

I&#39;m trying to call a class (main method) from command line (Windows) with Java.  
The class imports other classes (other jars).

I always get &quot;class not found exception&quot; from a class that my main program imports.

Here&#39;s what I tried:

- Add a CLASSPATH env. var with the path where the referenced lib resides (not working)

- I tried with all these different parameters when calling &quot;`java -jar myjar.jar`&quot; from command line : &quot;`-classpath lib/`&quot;, &quot;`-classpath ./lib/`&quot;, &quot;`-classpath lib`&quot;, &quot;`-cp lib/*`&quot;, &quot;`-cp lib/\*`&quot;, &quot;`-classpath lib/referenced-class.jar`&quot;, &quot;`-classpath ./lib/referenced-class.jar`&quot; (lib is where the referenced jar resides)

- I tried packaging all the referenced jar inside my jar where my main class resides...

- And with all that, I also tried to specify the classes inside the Manifest file with:
`Class-path referenced-jar.jar` and I also tried `Class-path lib/referenced-jar.jar`

Java: how to import a jar file from command line

What is the exact difference between these two interfaces? Does [`Enumeration`](http://docs.oracle.com/javase/7/docs/api/java/util/Enumeration.html) have benefits over using [`Iterator`](http://docs.oracle.com/javase/7/docs/api/java/util/Iterator.html)?  If anyone could elaborate, a reference article would be appreciated.

Difference between Java Enumeration and Iterator

What can you guys recommend to use with Java?

Only requirement is it should be open source, or has not too expensive academic licence .

Open Source Java Profilers

I want to check if an object `o` is an instance of the class `C` or of a subclass of `C`.

For instance, if `p` is of class `Point` I want `x.instanceOf(Point.class)` to be `true` and also `x.instanceOf(Object.class)` to be `true`.

I want it to work also for boxed primitive types. For instance, if `x` is an `Integer` then `x.instanceOf(Integer.class)` should be `true`.

Is there such a thing? If not, how can I implement such a method?

Is there something like instanceOf(Class&lt;?&gt; c) in Java?

I am looking for a tutorial/blog post on how to implement bittorrent protocol step by step.
How it works? How do you make requests to peers? and talk to trackers.

I do not mind the programming language (java,ruby,perl,c#)

Implementing Bittorrent Protocol

If I have a torrent w/o any trackers in it, and I just started a bittorent client so I have no peers yet...how do I know who to first connect with in the DHT?  It seems like I would have to know at least ONE node in the DHT to get started....

How does a DHT in a Bittorent client get &quot;bootstrapped&quot;?

For the first time I used a [magnet link](http://en.wikipedia.org/wiki/Magnet_URI_scheme). Curious about how it works, I looked up the specs and didn&#39;t find any answers. The wiki says `xt` means &quot;exact topic&quot; and is followed by the format (`btih` in this case) with a SHA1 hash. I saw base32 mentioned, knowing it&#39;s 5 bits per character and 32 characters, I found it holds exactly 160bits, which is exactly the size of the SHA1.

There&#39;s no room for an IP address or anything, it&#39;s just a SHA1. So how does the BitTorrent client find the actual file? I turned on URL Snooper to see if it visits a page (using TCP) or does a lookup or the like, but nothing happened. I have no idea how the client finds peers. How does this work?

Also, what is the hash of? Is it a hash of an array of all the file hashes together? Maybe it&#39;s a hash of the actual torrent file required (stripping certain information)?

---
In a VM, I tried a magnet link with uTorrent (which was freshly installed) and it managed to find peers. Where did the first peer come from? It was fresh and there were no other torrents.

How do BitTorrent magnet links work?

I started to explore the option of connecting with other using a p2p connection, so I coded a simple socket program in JAVA for android devices in which the users can share simple messages p2p (I didn&#39;t have any idea about NAT then). I got to know about NAT, so I now need to establish a TCP connection with another user which uses a server for discovery but payload is transferred p2p. I have also looked at XMPP(a very good and detailed explanation of how protocol works is [here][1]) and UPnP but I dont know how to implement them.

Another interesting question that arises is of BitTorrent because they can work on any device and even behind a NAT. I am not able to get any explanation of how BitTorrent works.

I have researched a lot but I am stuck.

My questions are:

1. A detailed explanation of BitTorrent(like [here][1], not how torrents work) and how is it able to work around NAT ?
2. Is there a way to make a NAT entry programmatically ?
3. Is socket programming sufficient for p2p ?
3. How difficult is it to create your own protocol and how can I build one ?
4. If two devices D1 and D2 want to communicate p2p and they know each other&#39;s IP. D1 sends a request to D2 and that can&#39;t get through the D2&#39;s NAT, but there should be an entry created in D1&#39;s NAT. So when D2 tries to send something D1&#39;s NAT should discover an entry with D2&#39;s IP. Then why is the packet not allowed by it ?


  [1]: http://ceit.uq.edu.au/content/how-xmpp-works-step-step

Connecting P2P over NAT?

I am trying to implement a [bittorrent tracker in Laravel][1]. However, I am stuck at the moment as the download won&#39;t start. There is one peer which it appears to be seeding and I am 100% sure that it is connectable. But, when I run a second client on a different machine, the download won&#39;t start. It is stuck at &quot;Connecting to peers&quot; (uTorrent).

From the tracker I am sending the following response when the client makes an announce:

    d8:intervali1000e12:min intervali300e5:peers18:�ؤ�i�ؑ�X&#218;JU�6e

In the downloading client I have the following data:

[![enter image description here][2]][2]
[![enter image description here][3]][3]

Here&#39;s my announce code:

    &lt;?php
    
    namespace App\Http\Controllers\Announce;
    
    use App\Helpers\BencodeHelper;
    use App\Models\Peer;
    use App\Models\PeerTorrent;
    use App\Models\Torrent;
    use App\Models\User;
    use Illuminate\Http\Request;
    use Illuminate\Http\Response;
    use Illuminate\Routing\Controller;
    use Illuminate\Support\Facades\Input;
    use Illuminate\Support\Facades\Log;
    
    class AnnounceController extends Controller
    {
        const __INTERVAL = 1000;
        const __TIMEOUT = 120;
        const __INTERVAL_MIN = 60;
        const __MAX_PPR = 20;
    
        public function announce(Request $request)
        {
            Log::info($request-&gt;fullUrl());
            $status = 200;
            $content = &quot;&quot;;
            $passkey = Input::get(&#39;passkey&#39;);
            $peer_id = Input::get(&#39;peer_id&#39;);
            $port = Input::get(&#39;port&#39;);
            $info_hash = Input::get(&#39;info_hash&#39;);
            $downloaded = Input::get(&#39;uploaded&#39;) ? intval(Input::get(&#39;uploaded&#39;)) : 0;
            $uploaded = Input::get(&#39;uploaded&#39;) ? intval(Input::get(&#39;uploaded&#39;)) : 0;
            $left = Input::get(&#39;left&#39;) ? intval(Input::get(&#39;left&#39;)) : 0;
            $compact = Input::get(&#39;compact&#39;) ? intval(Input::get(&#39;compact&#39;)) : 0;
            $no_peer_id = Input::get(&#39;no_peer_id&#39;) ? intval(Input::get(&#39;no_peer_id&#39;)) : 0;
    
            $ipAddress = &#39;&#39;;
            // Check for X-Forwarded-For headers and use those if found
            if (isset($_SERVER[&#39;HTTP_X_FORWARDED_FOR&#39;]) &amp;&amp; (&#39;&#39; !== trim($_SERVER[&#39;HTTP_X_FORWARDED_FOR&#39;]))) {
                $ipAddress = (trim($_SERVER[&#39;HTTP_X_FORWARDED_FOR&#39;]));
            } else {
                if (isset($_SERVER[&#39;REMOTE_ADDR&#39;]) &amp;&amp; (&#39;&#39; !== trim($_SERVER[&#39;REMOTE_ADDR&#39;]))) {
                    $ipAddress = (trim($_SERVER[&#39;REMOTE_ADDR&#39;]));
                }
            }
    
            $port = $_SERVER[&#39;REMOTE_PORT&#39;];
            /*if(!$port || !ctype_digit($port) || intval($port) &lt; 1 || intval($port) &gt; 65535)
            {
                $content = BencodeHelper::track(&quot;Invalid client port.&quot;);
                $status = 401;
                return (new Response(AnnounceController::track($content), $status))
                    -&gt;header(&#39;Content-Type&#39;, $value);
            }
    
            if ($port == 999 &amp;&amp; substr($peer_id, 0, 10) == &#39;-TO0001-XX&#39;) {
                die(&quot;d8:completei0e10:incompletei0e8:intervali600e12:min intervali60e5:peersld2:ip12:72.14.194.184:port3:999ed2:ip11:72.14.194.14:port3:999ed2:ip12:72.14.194.654:port3:999eee&quot;);
            }*/
    
    
            if (!$passkey) {
                $content = BencodeHelper::track(&quot;Missing passkey.&quot;);
                $status = 401;
                return (new Response(AnnounceController::track($content), $status))
                    -&gt;header(&#39;Content-Type&#39;, $value);
            }
    
    
            $torrent = Torrent::getByInfoHash(sha1($info_hash));
            if (!$torrent || $torrent == null) {
                $content = &quot;Torrent not registered with this tracker.&quot;;
                $status = 404;
                return (new Response(AnnounceController::track($content), $status))
                    -&gt;header(&#39;Content-Type&#39;, $value);
            }
    
            $user = User::has(&#39;passkeys&#39;, &#39;=&#39;, $passkey)-&gt;get();
    
            if ($user == null) {
                $content = BencodeHelper::track(&quot;Invalid passkey.&quot;);
                $status = 401;
                return (new Response(AnnounceController::track($content), $status))
                    -&gt;header(&#39;Content-Type&#39;, $value);
            }
    
            $peer = Peer::getByHashAndPasskey(bin2hex($peer_id), $passkey);
    
            if ($peer == null) {
                $peer = Peer::create([
                    &#39;hash&#39; =&gt; bin2hex($peer_id),
                    &#39;user_agent&#39; =&gt; $_SERVER[&#39;HTTP_USER_AGENT&#39;],
                    &#39;ip_address&#39; =&gt; $ipAddress,
                    &#39;passkey&#39; =&gt; $passkey,
                    &#39;port&#39; =&gt; $port
                ]);
            }
    
            if (!$info_hash || strlen($info_hash) != 20) {
                $content = BencodeHelper::track(&quot;Invalid info_hash.&quot;);
                $status = 401;
                return (new Response(AnnounceController::track($content), $status))
                    -&gt;header(&#39;Content-Type&#39;, $value);
            }
    
    
            $peer_torrent = PeerTorrent::getByPeerAndTorrent($peer, $torrent);
    
            if ($peer_torrent == null) {
                $peer_torrent = PeerTorrent::create([
                    &#39;peer_id&#39; =&gt; $peer-&gt;id,
                    &#39;torrent_id&#39; =&gt; $torrent-&gt;id,
                    &#39;uploaded&#39; =&gt; $uploaded,
                    &#39;downloaded&#39; =&gt; $downloaded,
                    &#39;left&#39; =&gt; $left,
                    &#39;stopped&#39; =&gt; false
                ]);
    
            } else {
                $peer_torrent-&gt;uploaded = $uploaded;
                $peer_torrent-&gt;downloaded = $downloaded;
                $peer_torrent-&gt;left = $left;
                $peer_torrent-&gt;save();
            }
    
            $seeders = $torrent-&gt;getSeedersCount();
            $leechers = $torrent-&gt;getLeechersCount();
            $resp = &quot;&quot;;
            if ($compact != 1) {
                $resp = &quot;d&quot; . $this-&gt;benc_str(&quot;interval&quot;) . &quot;i&quot; . AnnounceController::__INTERVAL . &quot;e&quot; . $this-&gt;benc_str(&quot;peers&quot;) . &quot;l&quot;;
            } else {
                $resp = &quot;d&quot; . $this-&gt;benc_str(&quot;interval&quot;) . &quot;i&quot; . AnnounceController::__INTERVAL . &quot;e&quot; . $this-&gt;benc_str(&quot;min interval&quot;) . &quot;i&quot; . 300 . &quot;e5:&quot; . &quot;peers&quot;;
            }
    
            $peer = array();
    
            $peer_num = 0;
            foreach ($torrent-&gt;getPeersArray() as $row) {
                if ($compact != 1) {
                    if ($row[&quot;peer_id&quot;] === $peer-&gt;hash) {
                        continue;
                    }
    
                    $resp .= &quot;d&quot; . $this-&gt;benc_str(&quot;ip&quot;) . $this-&gt;benc_str($row[&#39;ip&#39;]);
    
                    if ($no_peer_id == 0) {
                        $resp .= $this-&gt;benc_str(&quot;peer id&quot;) . $this-&gt;benc_str($row[&quot;peer_id&quot;]);
                    }
    
                    $resp .= $this-&gt;benc_str(&quot;port&quot;) . &quot;i&quot; . $row[&quot;port&quot;] . &quot;e&quot; . &quot;e&quot;;
    
                } else {
                    $peer_ip = explode(&#39;.&#39;, $row[&quot;ip&quot;]);
                    $peer_ip = pack(&quot;C*&quot;, $peer_ip[0], $peer_ip[1], $peer_ip[2], $peer_ip[3]);
                    $peer_port = pack(&quot;n*&quot;, (int)$row[&quot;port&quot;]);
                    $time = intval((time() % 7680) / 60);
    
                    if ($left == 0) {
                        $time += 128;
                    }
    
                    $time = pack(&quot;C&quot;, $time);
                    $peer[] = $time . $peer_ip . $peer_port;
                    $peer_num++;
                }
            }
    
            if ($compact != 1) {
                $resp .= &quot;ee&quot;;
            } else {
                $o = &quot;&quot;;
                for ($i = 0; $i &lt; $peer_num; $i++) {
                    $o .= substr($peer[$i], 1, 6);
                }
                $resp .= strlen($o) . &#39;:&#39; . $o . &#39;e&#39;;
            }
    
            $this-&gt;benc_resp_raw($resp);
        }
    
        public function benc_resp($d)
        {
            return $this-&gt;benc_resp_raw($this-&gt;benc(array(&#39;type&#39; =&gt; &#39;dictionary&#39;, &#39;value&#39; =&gt; $d)));
        }
    
        public function benc_resp_raw($x)
        {
            header(&quot;Content-Type: text/plain&quot;);
            header(&quot;Pragma: no-cache&quot;);
    
            if ($_SERVER[&#39;HTTP_ACCEPT_ENCODING&#39;] == &#39;gzip&#39;) {
                header(&quot;Content-Encoding: gzip&quot;);
                echo gzencode($x, 9, FORCE_GZIP);
            } else {
                echo $x;
            }
        }
    
        function benc($obj)
        {
            if (!is_array($obj) || !isset($obj[&quot;type&quot;]) || !isset($obj[&quot;value&quot;]))
                return;
            $c = $obj[&quot;value&quot;];
            switch ($obj[&quot;type&quot;]) {
                case &quot;string&quot;:
                    return $this-&gt;benc_str($c);
                case &quot;integer&quot;:
                    return $this-&gt;benc_int($c);
                case &quot;list&quot;:
                    return $this-&gt;benc_list($c);
                case &quot;dictionary&quot;:
                    return $this-&gt;benc_dict($c);
                default:
                    return;
            }
        }
    
        public function benc_str($s)
        {
            return strlen($s) . &quot;:$s&quot;;
        }
    
        public function benc_int($i)
        {
            return &quot;i&quot; . $i . &quot;e&quot;;
        }
    
        public function benc_list($a)
        {
            $s = &quot;l&quot;;
            foreach ($a as $e) {
                $s .= $this-&gt;benc($e);
            }
            $s .= &quot;e&quot;;
            return $s;
        }
    
        public function benc_dict($d)
        {
            $s = &quot;d&quot;;
            $keys = array_keys($d);
            sort($keys);
            foreach ($keys as $k) {
                $v = $d[$k];
                $s .= $this-&gt;benc_str($k);
                $s .= $this-&gt;benc($v);
            }
            $s .= &quot;e&quot;;
            return $s;
        }
    
    
        public function hex2bin($hex)
        {
            $r = &#39;&#39;;
            for ($i = 0; $i &lt; strlen($hex); $i += 2) {
                $r .= chr(hexdec($hex{$i} . $hex{($i + 1)}));
            }
            return $r;
        }
    }

I am not quite sure what am I missing here.


  [1]: https://github.com/Comforse/laratracker
  [2]: http://i.stack.imgur.com/ix44c.png
  [3]: http://i.stack.imgur.com/5vFNp.png

Content Type	Original Author	Original Content on Stackoverflow
Question	samulisoderlund	View Question on Stackoverflow
Solution 1 - Java	leonm	View Answer on Stackoverflow
Solution 2 - Java	jjnguy	View Answer on Stackoverflow
Solution 3 - Java	Toilal	View Answer on Stackoverflow
Solution 4 - Java	Anonymous	View Answer on Stackoverflow
Solution 5 - Java	Thorbjørn Ravn Andersen	View Answer on Stackoverflow
Solution 6 - Java	Anirudh	View Answer on Stackoverflow
Solution 7 - Java	Mateu	View Answer on Stackoverflow

Java BitTorrent library

Java Problem Overview

Java Solutions

Solution 1 - Java

Solution 2 - Java

Solution 3 - Java

Solution 4 - Java

Solution 5 - Java

Solution 6 - Java

Solution 7 - Java

How to send an HTTPS GET Request in C#

C# automatic property deserialization of JSON

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