Network.BitTorrent.Core.PeerId

PeerID represent self assigned peer identificator. Ideally each host in the network should have unique peer id to avoid collisions, therefore for peer ID generation we use good entropy source. (FIX not really) Peer ID is sent in tracker request, sent and received in peer handshakes and used in /distributed hash table/ queries.

PeerId

data PeerId

Peer identifier is exactly 20 bytes long bytestring.

Instances

Eq PeerId

Ord PeerId

Show PeerId

IsString PeerId

ToJSON PeerId

FromJSON PeerId

S.Serialize PeerId

URLShow PeerId

Pretty PeerId

BEncode PeerId

Generation

genPeerId :: IO PeerId

Here we use Azureus-style encoding with the following args:

• HS for the client id.
• Version of the package for the version number
• UTC time day ++ day time for the random number.

timestamp :: IO BS.ByteString

Gives 15 characters long decimal timestamp such that:

• 6 bytes : first 6 characters from picoseconds obtained with %q.
• 1 bytes : character . for readability.
• 9..* bytes: number of whole seconds since the Unix epoch (!)REVERSED.

Can be used both with shadow and azureus style encoding. This format is used to make the ID's readable(for debugging) and more or less random.

entropy :: IO BS.ByteString

Gives 15 character long random bytestring. This is more robust method for generation of random part of peer ID than timestamp.

Encoding

azureusStyle

Arguments

:: BS.ByteString

2 character client ID, padded with H.

-> BS.ByteString

Version number, padded with X.

-> BS.ByteString

Random number, padded with '0'.

-> PeerId

Azureus-style encoded peer ID.

Azureus-style encoding have the following layout:

• 1 byte : -
• 2 bytes: client id
• 4 bytes: version number
• 1 byte : -
• 12 bytes: random number

shadowStyle

Arguments

:: Char

Client ID.

-> BS.ByteString

Version number.

-> BS.ByteString

Random number.

-> PeerId

Shadow style encoded peer ID.

Shadow-style encoding have the following layout:

• 1 byte : client id.
• 0-4 bytes: version number. If less than 4 then padded with - char.
• 15 bytes : random number. If length is less than 15 then padded with '0' char.

Decoding

clientInfo :: PeerId -> ClientInfo

Tries to extract meaningful information from peer ID bytes. If peer id uses unknown coding style then client info returned is def.

Extra

byteStringPadded

Arguments

:: BS.ByteString

bytestring to be padded.

-> Int

size of result builder.

-> Char

character used for padding.

-> BS.Builder

Pad bytestring so it's becomes exactly request length. Conversion is done like so:

• length < size: Complete bytestring by given charaters.
• length = size: Output bytestring as is.
• length > size: Drop last (length - size) charaters from a given bytestring.

defaultClientId :: BS.ByteString

HS - 2 bytes long client identifier.

defaultVersionNumber :: BS.ByteString

Gives exactly 4 bytes long version number for any version of the package. Version is taken from .cabal.