the complete description of bittorrent protocol:

http://jonas.nitro.dk/bittorrent/bittorrent-rfc.html

There is the [libtorrent][1] library.

Here&#39;s the [API documentation][2] and [examples][3].


  [1]: http://www.rasterbar.com/products/libtorrent/index.html
  [2]: http://www.rasterbar.com/products/libtorrent/manual.html
  [3]: http://www.rasterbar.com/products/libtorrent/examples.html

This is good source http://www.kristenwidman.com/blog/how-to-write-a-bittorrent-client-part-1/
She explains the process step by step...

I&#39;d suggest you look [at the spec][1] and sources of some OSS clients. You&#39;ll have to do some work, but that&#39;s how programming works.

  [1]: http://www.bittorrent.org/beps/bep_0003.html

I&#39;m currently implementing a BitTorrent client in Java using [this][1] specification.

[1]: http://wiki.theory.org/index.php/BitTorrentSpecification

Qt is very easy to read so you can read the [Qt Torrent Example][1] (C++)


  [1]: https://doc.qt.io/qt-5/qtnetwork-torrent-example.html

This is a implementation of the bittorrent protocol done in .NET. Its source code is available on github and it has documentation

[Monotorrent][1]


  [1]: http://www.monotorrent.com/

Implementing the protocol is not that hard by following the specs. However, there are lots of internal things like storage, scalable server, peer/piece pick algorithm, etc. 

Earlier BitTorrent implementation or [BitTornado][1] used python, which is easy to read. I personally found them useful to understand the internals.


  [1]: http://www.bittornado.com

I&#39;m new to Objective C and I haven&#39;t been able to find out if there is the equivalent of a static constructor in the language, that is a static method in a class that will automatically be called before the first instance of such class is instantiated. Or do I need to call the Initialization code myself?

Thanks

Static constructor equivalent in Objective-C?

I manage a group of programmers. I do value my employees opinion but lately we&#39;ve been divided as to which framework to use on web projects.

I personally favor **[MooTools][1]**, but some of my team seems to want to migrate to [jQuery][2] because it is more widely adopted. That by itself is not enough for me to allow a migration.

I have used both **[jQuery][2]** and **[MooTools][1]**. [This particular essay][3] tends to reflect how I feel about both frameworks. **[jQuery][2]** is great for DOM Manipulation, but seem to be limited to helping you do that.

Feature wise, both **[jQuery][2]** and **[MooTools][1]** allow for easy **DOM Selection and Manipulation**:

    // jQuery
    $(&#39;#someContainer div[class~=dialog]&#39;)
        .css(&#39;border&#39;, &#39;2px solid red&#39;)
        .addClass(&#39;critical&#39;);

    // MooTools
    $(&#39;#someContainer div[class~=dialog]&#39;)
        .setStyle(&#39;border&#39;, &#39;2px solid red&#39;)
        .addClass(&#39;critical&#39;);


Both **[jQuery][2]** and **[MooTools][1]** allow for easy **AJAX**:

    // jQuery
    $(&#39;#someContainer div[class~=dialog]&#39;)
         .load(&#39;/DialogContent.html&#39;);
    
    // MooTools (Using shorthand notation, you can also use Request.HTML)
    $(&#39;#someContainer div[class~=dialog]&#39;)
         .load(&#39;/DialogContent.html&#39;);

Both **[jQuery][2]** and **[MooTools][1]** allow for easy **DOM Animation**:

    // jQuery
    $(&#39;#someContainer div[class~=dialog]&#39;)
        .animate({opacity: 1}, 500);
    
    // MooTools (Using shorthand notation, you can also use Fx.Tween).
    $(&#39;#someContainer div[class~=dialog]&#39;)
        .set(&#39;tween&#39;, {duration: 500}) 
        .tween(&#39;opacity&#39;, 1);

**[jQuery][2]** offers the following extras:

 - Large community of supporters
 - Plugin Repository
 - Integration with Microsoft&#39;s ASP.NET and VisualStudio
 - Used by Microsoft, Google and others

**[MooTools][1]** offers the following extras:

 - Object Oriented Framework with Classic OOP emulation for JS
 - Extended native objects
 - Higher consistency between browsers for native functions support.
 - More easy code reuse
 - Used by The World Wide Web Consortium, Palm and others.

Given that, it seems that **[MooTools][1]** does everything **[jQuery][2]** does and more (some things I cannot do in **[jQuery][2]** and I can in **[MooTools][1]**) but **[jQuery][2]** has a smaller learning curve.

So the question is, why did you or your team choose **[jQuery][2]** over another JavaScript framework?

**Note:** While I know and admit **[jQuery][2]** is a great framework, there are other options around and I&#39;m trying to take a decision as to why **[jQuery][2]** should be our choice versus what we use right now (**[MooTools][1]**)?

  [1]: http://mootools.net/
  [2]: http://jquery.com/
  [3]: http://jqueryvsmootools.com/

Why is jQuery so widely adopted versus other Javascript frameworks?

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

<p>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.</p>
<p>I do not mind the programming language (java,ruby,perl,c#)</p>


I&#39;m coding a p2p implementation that I would like to make decentralized however I&#39;m having some trouble grasping how DHT in protocols like bittorrent work. How does the client know where the peers are if there is no tracker? Are peers stored in the actual torrent file?

How does DHT in torrents work?

What are the pros and cons of each of them?    
Where should I use them specifically?

NSNotificationCenter vs delegation( using protocols )?

There are four common protocols for network access of SVN.

    svn://repos
    svn+ssh://repos
    https://repos
    http://repos

The Wikipedia page doesn&#39;t say much about the differences of the four different protocols. I&#39;ve always preferred `svn://`, because it is the easiest to set up, but what is the difference and which one is &quot;better&quot;?


Which protocol? svn:// or http(s)://?

does anyone have a good definition for what a binary protocol is? and what is a text protocol actually? how do these compare to each other in terms of bits sent on the wire? 

here&#39;s what wikipedia says about binary protocols:

A binary protocol is a protocol which is intended or expected to be read by a machine rather than a human being (http://en.wikipedia.org/wiki/Binary_protocol)

oh come on! 

to be more clear, if I have jpg file how would that be sent through a binary protocol and how through a text one? in terms of bits/bytes sent on the wire of course. 

at the end of the day if you look at a string it is itself an array of bytes so the distinction between the 2 protocols should rest on what actual data is being sent on the wire. in other words, on how the initial data (jpg file) is encoded before being sent.



binary protocols v. text protocols

I&#39;m trying to understand clojure protocols and what problem they are supposed to solve. Does anyone have a clear explanation of the whats and whys of clojure protocols?

Simple explanation of clojure protocols

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	Hamza Yerlikaya	View Question on Stackoverflow
Solution 1 - Protocols	pesarak	View Answer on Stackoverflow
Solution 2 - Protocols	Jonathan Prior	View Answer on Stackoverflow
Solution 3 - Protocols	Bhushan Lodha	View Answer on Stackoverflow
Solution 4 - Protocols	Armandas	View Answer on Stackoverflow
Solution 5 - Protocols	macbirdie	View Answer on Stackoverflow
Solution 6 - Protocols	Derick Schoonbee	View Answer on Stackoverflow
Solution 7 - Protocols	blessanm86	View Answer on Stackoverflow
Solution 8 - Protocols	goododd	View Answer on Stackoverflow

Implementing Bittorrent Protocol

Protocols Problem Overview

Protocols Solutions

Solution 1 - Protocols

Solution 2 - Protocols

Solution 3 - Protocols

Solution 4 - Protocols

Solution 5 - Protocols

Solution 6 - Protocols

Solution 7 - Protocols

Solution 8 - Protocols

Why is jQuery so widely adopted versus other Javascript frameworks?

Static constructor equivalent in Objective-C?

Attributions