anchor.diff:  %% Tests
   %% ----------------------------------------------------------------------
   groups() ->
  -    Tests = [down_udp_tracker,
  -             choked_seed_leech, seed_transmission, leech_transmission,
  -             seed_leech, partial_downloading, udp_seed_leech, bep9],
  +    Tests = [choked_seed_leech, seed_transmission, leech_transmission,
  +             seed_leech, partial_downloading, udp_seed_leech, bep9,
  +             down_udp_tracker],
   %   [{main_group, [shuffle], Tests}].
       [{main_group, [], Tests}].
   
  
positive.code:      {leech_node_dir, LNodeDir} | Config];
  init_per_testcase(down_udp_tracker, Config) ->
      PrivDir   = ?config(priv_dir, Config),
      DataDir   = ?config(data_dir, Config),
      LNode     = ?config(leech_node, Config),
      LNodeDir = filename:join([PrivDir,  leech]),
      create_standard_directory_layout(LNodeDir),
  
negative.code:     io:format("~n======START SLOW SEED AND LEECHING TEST CASE======~n", []),
      {Ref, Pid} = {make_ref(), self()},
  
      CNode = ?config(choked_seed_node, Config),
      LNode = ?config(leech_node, Config),
      SNode = ?config(seed_node, Config),
      BinIH = ?config(info_hash_bin, Config),
      CTorrentID = wait_torrent_registration(CNode, BinIH),
      STorrentID = wait_torrent_registration(SNode, BinIH),
      io:format("TorrentID on the choked_seed node is ~p.~n", [CTorrentID]),
  
      {ok, LTorrentID} = rpc:call(LNode, etorrent, start,
  		  [?config(http_torrent_file, Config), {Ref, Pid}]),
  
      io:format("TorrentID on the leech node is ~p.~n", [LTorrentID]),
  
      %% Leech peer control process on the slow node.
      LeechId  = rpc:call(LNode, etorrent_ctl, local_peer_id, []),
      CPeerPid = wait_peer_registration(CNode, CTorrentID, LeechId),
      SPeerPid = wait_peer_registration(SNode, STorrentID, LeechId),
      io:format("Peer registered.~n", []),
      rpc:call(SNode, etorrent_peer_control, choke, [SPeerPid]),
  
      wait_torrent(LNode, LTorrentID),
      wait_progress(LNode, LTorrentID, 50),
      io:format("50% were downloaded.~n", []),
  
      true = is_fast_peer(CNode, CPeerPid),
      io:format("Using fast protocol.~n", []),
  
  
      choke_in_the_middle(CNode, CPeerPid),
      io:format("Leecher choked.~n", []),
  
      %% Let the leacher to download the torrent from SNode.
      rpc:call(SNode, etorrent_peer_control, unchoke, [SPeerPid]),
  
      receive
  	{Ref, done} -> ok
  