webtorrent-dht

webtorrent-dht

This is an example implementation of something that might become WebTorrent DHT. It is based on BitTorrent DHT and is extended in a way that will work both in Node.js and modern browsers while keeping BitTorrent DHT interface.

This project is WIP and not ready for production use.

How to use

Assuming you're familiar with bittorrent-dht usage is the same with 2 differences: bootstrap nodes are WebSocket nodes and by binding to address and port effectively WebSocket server is started. Everything else is happening under the hood.

Also K in WebTorrent DHT defaults to 2, which is much more reasonable for WebRTC realities.

Additional options specific to WebTorrent DHT are:

• extensions - Array of strings with extensions supported by current node
• simple_peer_opts - Object as in simple-peer constructor, used by webrtc-socket
• simple_peer_constructor - Custom implementation of simple-peer, in case it is necessary
• ws_address - Object with keys address and port that corresponds to running WebSocket server (specify this in case when publicly accessible address/port are different from those where WebSocket server is listening on), used by webrtc-socket

There are simple demos in demo directory, you can run them in browser and on the server and then use dht key on window or global for DHT queries.

For debugging purposes run on Node as following:

DEBUG=webtorrent-dht node demo/node-server.js 

And set on client debug localStorage key as following:

localStorage.debug = 'webtorrent-dht'

This will output a lot of useful debugging information.

How it works

This project in composed of 4 components as following:

• webtorrent-dht inherits bittorrent-dht
• k-rpc-webrtc inherits k-rpc
• k-rpc-socket-webrtc inherits k-rpc-socket
• webrtc-socket (superset of the subset of dgram interface implemented from scratch)

For high level protocol extension description in form of potential BEP take a look at bep.rts file in this repository.

webtorrent-dht

Uses k-rpc-webrtc instance instead of k-rpc in constructor.

Patches its toJSON() method of bittorrent-dht so that nodes property of returned object contains WebSockets nodes only. This ensures that bootstrapping will be possible from those nodes in future (WebRTC-only nodes can't be used for this since they require 2-way signaling before connection can be established).

Also listen() method is now used to start WebSocket server, but this will be detailed in webrtc-socket component.

Other than mentioned changes webtorrent-dht API is exactly the same as bittorrent-dht.

This is the components exported by this package.

k-rpc-webrtc

Uses k-rpc-socket-webrtc instance instead of k-rpc-socket in constructor.

Uses other default bootstrap nodes than k-rpc.

Forgets about disconnected nodes as soon as disconnection happens (since we know when this happens exactly).

k-rpc-socket-webrtc

Uses socket-webrtc instance instead of dgram in constructor.

Patches send() method for logging in debug mode.

Patches query() method for find_node, get_peer and get queries by injecting signals argument with WebRTC offer signaling data before making query and establishes WebRTC connection when response to the query with WebRTC answer signaling data is received. Also each peer in nodes and values keys from response is updated with IP address and port of the actual established WebRTC connection (since response will contain details of the queried node and those details will likely be slightly different).

Patches response() method for find_node, get_peer and get queries by re-sending WebRTC offer signaling data to the peers queried node is about to respond with (using peer_connection query) and injects signals key into the response with WebRTC answer signaling data and same number of entries and order as corresponding nodes or values key.

Patches emit method to capture firing query event for peer_connection query and handles it itself (while not canceling query event as such) by consuming WebRTC offer signaling data and responding with WebRTC answer signaling data. Also associates nodes IDs with corresponding WebRTC peers connections.

webrtc-socket

Implements the subset of dgram interface (address, bind, close, emit, on and send methods) as used by k-rpc-socket (exactly what is used, nothing more) and superset on top of it with features used by k-rpc-socket-webrtc and webtorrent-dht.

• address method returns information about where WebSocket server is listening, object with keys address and port
• bind method starts WebSocket server on specified address and port (both should be specified explicitly)
• close method closes all WebRTC connections and stops WebSocket server if it is running
• emit method emits an event with arguments
• on method adds handler for an event
• send method first checks if there is an established WebRTC connection to specified address and port, if not - assumes WebSocket address and port were specified, so that it will establish WebSocket connection, use it for establishing WebRTC connection, will close WebSocket connection and create an alias to use WebRTC connection instead next time

There are a few of public methods exposed by webrtc-socket:

• get_id_mapping(id : string) - Allows to get simple-peer instance by node's ID if connection is already established
• add_tag(id : string, association : string) - Allows to tag connection to specified node ID so that connection will not be closed until at least one tag is left
• del_tag(id : string, association : string) - Remove tag from connection to specified node ID, if no tags left on connection - it will be closed

There are also a few events exposed by webrtc-socket:

• node_connected with string argument id - Is fired when there is a new connection established
• node_disconnected with string argument id - Is fired when there is a connection was closed
• extensions_received with arguments peer_connection (simple-peer instance) and an array extensions - If fired when extensions are received from the other peer
• websocket_peer_connection_alias with arguments host, port and peer_connection - Is fired when peer connection is aliased by websocket host and port (from bootstrap node)

Contribution

Feel free to create issues and send pull requests (for big changes create an issue first and link it from the PR), they are highly appreciated!

License

Free Public License 1.0.0 / Zero Clause BSD License

https://opensource.org/licenses/FPL-1.0.0

https://tldrlegal.com/license/bsd-0-clause-license