title: Bittorrent UDP implementation
body: <p>Can someone point me to some documentation on how to implement a Bittorrent UDP application?<br>
  I am working on a Bittorrent application and I can successfully download using TCP but I want to implement UDP and I can't find any information on it.  I am retrieving peers with UDP trackers but that approach appears different than downloading files.
  If I sniff a UDP Handshake I see the following in Wireshark:</p>
  
  <p>172.16.49.213  5.31.44.30   UDP 62  35507 → 18318 Len=20</p>
  
  <p>5.31.44.30 172.16.49.213   UDP 62  18318 → 35507 Len=20</p>
  
  <p>This is done before the handshake.  Also, it looks like there are 20 bytes prepended to the Handshake (different than the 20 bytes above).</p>
  
  <p>So I need some information to help me with what all this means.</p>