NAME

  Net::BitTorrent::PeerPacket - Parse/Build Peer Packets from BitTorrent

SYNOPSIS

  # import everything
  use Net::BitTorrent::PeerPacket qw(:all);

  # or be more selective
  use Net::BitTorrent::PeerPacket qw(bt_build_packet :constants);

  # Encode a packet
  my $binary_packet = bt_build_packet($key1, $value1, $key2, $value2);

  # Decode a packet
  my $parsed_packet = bt_parse_packet($binary_data);

DESCRIPTION

"Net::BitTorrent::PeerPacket" handles parsing and building binary data shared between BitTorrent peers. The module optionally exports a single subroutine for building packets and another for parsing packets, as well as, a constant for each packet type defined by BitTorrent.

CONSTANTS

There are ten primary types of packets that are shared between peers on a BitTorrent network. The following constants are how the type of packet being build/parsed are represented within this module.

BT_HANDSHAKE: Used to start communication between peers.
BT_CHOKE: Tell a peer that it is choked.
BT_UNCHOKE: Tell a peer that it is unchoked.
BT_INTERESTED: Used to tell a peer that it has a piece that you need.
BT_UNINTERESTED: Used to tell a peer that it has no pieces that you need.
BT_HAVE: Used to tell a peer that you now have a specific piece.
BT_BITFIELD: Used right after a handshake, this tells a peer all of the pieces that you have and don't have in one message.
BT_REQUEST: Used to request a block of data from a piece that a peer has.
BT_PIECE: Used to return a block of data that was requested.
BT_CANCEL: Used to tell a peer that you no longer need the piece that you were downloading from them.

SUBROUTINES

bt_build_packet

This subroutine is responsible for building all types of BitTorrent packets. The arguments are passed into the subroutine as a list of key-value pairs. The resultant packet is sent back as a scalar.

Depending on the requested packet type, the required arguments vary. One argument that is common to all calls is the "bt_code". The "bt_code" maps to a "BT_" constant exported by this module and determines the type of packet that will be built.

What follows is a list of the different BT codes and the details of calling this subroutine with those codes.

BT_HANDSHAKE

Passing the "BT_HANDSHAKE" code causes a handshake packet to be generated. This type of packet is sent as soon as peers are connected and requires two additional keys:

info_hash
The hash found in the ".torrent" file that represents the download.
peer_id
The peer ID for the local peer. This should be the same as what is reported to the tracker for the swarm.

BT_CHOKE

Passing the "BT_CHOKE" code causes a choke packet to be generated. This type of packet requires no additional data and therefore no additional arguments.

BT_UNCHOKE

Passing the "BT_UNCHOKE" code causes an unchoke packet to be generated. This type of packet requires no additional data and therefore no additional arguments.

BT_INTERESTED

Passing the "BT_INTERESTED" code causes an interested packet to be generated. This type of packet requires no additional data and therefore no additional arguments.

BT_UNINTERESTED

Passing the "BT_UNINTERESTED" code causes an uninterested packet to be generated. This type of packet requires no additional data and therefore no additional arguments.

BT_HAVE

Passing the "BT_HAVE" code causes a have packet to be generated. This type of packet requires a piece index in addition to the BT code.

piece_index: The piece index is the zero-based numeric index of a piece within a torrent.

BT_BITFIELD

Passing the "BT_BITFIELD" code causes a bit field packet to be generated. This type of packet requires the bit field be specified in addition to the BT code.

bitfield_ref: The bit field is passed in as a reference to a scalar. The scalar contains binary data representing the pieces that are present and missing.

BT_REQUEST

Passing the "BT_REQUEST" code causes a request packet to be generated. This type of packet requires the piece index along with block offset and size in addition to the BT code.

piece_index: The piece index is the zero-based numeric index of a piece within a torrent.
block_offset: The block offset is the zero-based byte offset of the requested data within the specified piece.
block_size: The block size is the size of the data requested. Be sure not to set this value too large, as some clients will end your connection if your request is too big.

BT_PIECE

Passing the "BT_PIECE" code causes a piece packet to be generated. This type of packet requires the piece index along with block offset and the data to be transferred in addition to the BT code.

piece_index: The piece index is the zero-based numeric index of a piece within a torrent.
block_offset: The block offset is the zero-based byte offset of the requested data within the specified piece.
data_ref: The data reference is a reference to a scalar containing the data at the specified block offset within the specified piece.

BT_CANCEL

Passing the "BT_CANCEL" code causes a cancel packet to be generated. This type of packet requires the piece index along with block offset and size in addition to the BT code.

piece_index: The piece index is the zero-based numeric index of a piece within a torrent.
block_offset: The block offset is the zero-based byte offset of the requested data within the specified piece.
block_size: The block size is the size of the data requested. Be sure not to set this value too large, as some clients will end your connection if your request is too big.

bt_parse_packet

This subroutine is responsible for parsing all types of BitTorrent packets. It accepts a single argument, which is a reference to a scalar that contains the raw packet data. It returns a hash reference containing the parsed data.

Depending on the packet type, the keys in the returned hash vary. One key that is common to all packets is the bt_code. The bt_code maps to a BT_ constant exported by this module and reveals the type of packet that was parsed.

What follows is a list of the different BT codes that might be returned and the additional keys that will be packaged with each code.

BT_CHOKE

The resultant hash from a choke packet will only contain the "bt_code" key.

BT_UNCHOKE

The resultant hash from an unchoke packet will only contain the "bt_code" key.

BT_INTERESTED

The resultant hash from an interested packet will only contain the "bt_code" key.

BT_UNINTERESTED

The resultant hash from an uninterested packet will only contain the "bt_code" key.

BT_HAVE

The resultant hash from a have packet will only contain the "bt_code" key and the following additional keys.

piece_index: The piece index is the zero-based numeric index of a piece within a torrent.

BT_BITFIELD

The resultant hash from a bit field packet will only contain the "bt_code" key and the following additional keys.

bitfield_ref: The bit field is passed in as a reference to a scalar. The scalar contains binary data representing the pieces that are present and missing.

BT_REQUEST

The resultant hash from a request packet will only contain the "bt_code" key and the following additional keys.

piece_index: The piece index is the zero-based numeric index of a piece within a torrent.
block_offset: The block offset is the zero-based byte offset of the requested data within the specified piece.
block_size: The block size is the size of the data requested. Be sure not to set this value too large, as some clients will end your connection if your request is too big.

BT_PIECE

The resultant hash from a piece packet will only contain the "bt_code" key and the following additional keys.

piece_index: The piece index is the zero-based numeric index of a piece within a torrent.
block_offset: The block offset is the zero-based byte offset of the requested data within the specified piece.
data_ref: The data reference is a reference to a scalar containing the data at the specified block offset within the specified piece.

BT_CANCEL

The resultant hash from a cancel packet will only contain the "bt_code" key and the following additional keys.

piece_index: The piece index is the zero-based numeric index of a piece within a torrent.
block_offset: The block offset is the zero-based byte offset of the requested data within the specified piece.
block_size: The block size is the size of the data requested. Be sure not to set this value too large, as some clients will end your connection if your request is too big.

INSTALL

  perl Build.PL
  ./Build
  ./Build test
  ./Build install

AUTHOR

Josh McAdams <joshua dot mcadams at gmail dot com>