Net-BitTorrent-PeerPacket

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>