This is an I2P port of snark [http://klomp.org/snark], a GPL'ed bittorrent client

The build in tracker has been removed for simplicity.

Example usage:
  java -jar lib/i2psnark.jar myFile.torrent

or, a more verbose setting:
  java -jar lib/i2psnark.jar --eepproxy 127.0.0.1 4444 \
       --i2cp 127.0.0.1 7654 "inbound.length=2 outbound.length=2" \
       --debug 6 myFile.torrent

apps/i2psnark/java/src/org/klomp/snark/Message.java

@@ -0,0 +1,137 @@
+/* Message - A protocol message which can be send through a DataOutputStream.
+   Copyright (C) 2003 Mark J. Wielaard
+
+   This file is part of Snark.
+   
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+ 
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+ 
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+*/
+
+package org.klomp.snark;
+
+import java.io.DataOutputStream;
+import java.io.IOException;
+
+// Used to queue outgoing connections
+// sendMessage() should be used to translate them to wire format.
+class Message
+{
+  final static byte KEEP_ALIVE   = -1;
+  final static byte CHOKE        = 0;
+  final static byte UNCHOKE      = 1;
+  final static byte INTERESTED   = 2;
+  final static byte UNINTERESTED = 3;
+  final static byte HAVE         = 4;
+  final static byte BITFIELD     = 5;
+  final static byte REQUEST      = 6;
+  final static byte PIECE        = 7;
+  final static byte CANCEL       = 8;
+  
+  // Not all fields are used for every message.
+  // KEEP_ALIVE doesn't have a real wire representation
+  byte type;
+
+  // Used for HAVE, REQUEST, PIECE and CANCEL messages.
+  int piece;
+
+  // Used for REQUEST, PIECE and CANCEL messages.
+  int begin;
+  int length;
+
+  // Used for PIECE and BITFIELD messages
+  byte[] data;
+  int off;
+  int len;
+
+  /** Utility method for sending a message through a DataStream. */
+  void sendMessage(DataOutputStream dos) throws IOException
+  {
+    // KEEP_ALIVE is special.
+    if (type == KEEP_ALIVE)
+      {
+        dos.writeInt(0);
+        return;
+      }
+
+    // Calculate the total length in bytes
+
+    // Type is one byte.
+    int datalen = 1;
+
+    // piece is 4 bytes.
+    if (type == HAVE || type == REQUEST || type == PIECE || type == CANCEL)
+      datalen += 4;
+
+    // begin/offset is 4 bytes
+    if (type == REQUEST || type == PIECE || type == CANCEL)
+      datalen += 4;
+
+    // length is 4 bytes
+    if (type == REQUEST || type == CANCEL)
+      datalen += 4;
+
+    // add length of data for piece or bitfield array.
+    if (type == BITFIELD || type == PIECE)
+      datalen += len;
+
+    // Send length
+    dos.writeInt(datalen);
+    dos.writeByte(type & 0xFF);
+
+    // Send additional info (piece number)
+    if (type == HAVE || type == REQUEST || type == PIECE || type == CANCEL)
+      dos.writeInt(piece);
+
+    // Send additional info (begin/offset)
+    if (type == REQUEST || type == PIECE || type == CANCEL)
+      dos.writeInt(begin);
+
+    // Send additional info (length); for PIECE this is implicit.
+    if (type == REQUEST || type == CANCEL)
+        dos.writeInt(length);
+
+    // Send actual data
+    if (type == BITFIELD || type == PIECE)
+      dos.write(data, off, len);
+  }
+
+  public String toString()
+  {
+    switch (type)
+      {
+      case KEEP_ALIVE:
+        return "KEEP_ALIVE";
+      case CHOKE:
+        return "CHOKE";
+      case UNCHOKE:
+        return "UNCHOKE";
+      case INTERESTED:
+        return "INTERESTED";
+      case UNINTERESTED:
+        return "UNINTERESTED";
+      case HAVE:
+        return "HAVE(" + piece + ")";
+      case BITFIELD:
+        return "BITFIELD";
+      case REQUEST:
+        return "REQUEST(" + piece + "," + begin + "," + length + ")";
+      case PIECE:
+        return "PIECE(" + piece + "," + begin + "," + length + ")";
+      case CANCEL:
+        return "CANCEL(" + piece + "," + begin + "," + length + ")";
+      default:
+        return "<UNKNOWN>";
+      }
+  }
+}