secjs-devp2p

This library bundles different components for lower-level peer-to-peer connection and message exchange:

• Distributed Peer Table (NDP) / Node Discovery
• RLP Transport Protocol (secjs-rlp)
• SEC Wire Protocol (SEC)

Run/Build

This library has to be compiled with babel to a Node 6 friendly source format. For triggering a (first) build to create the lib/ directory run:

npm run build

You can also use babel just-in-time compilation to run a script:

node -r babel-register [YOUR_SCRIPT_TO_RUN.js]

Usage/Examples

All components of this library are implemented as Node EventEmitter objects and make heavy use of the Node.js network stack.

You can react on events from the network like this:

ndp.on('peer:added', (peer) => {
  // Your Codes...
})

Distributed Peer Table / Node Discovery Protocol (NDP)

Maintain/manage a list of peers, see ./src/ndp/, also includes node discovery (./src/ndp/server.js)

Usage

Create your peer table:

const ndp = new NDP(Buffer.from(PRIVATE_KEY, 'hex'), {
  endpoint: {
    address: '0.0.0.0',
    udpPort: null,
    tcpPort: null
  }
})

API

NDP (extends EventEmitter)

NDP Manages a Kademlia DHT K-bucket for storing peer information and a BanList for keeping a list of bad peers. server.js implements the node discovery (ping, pong, findNeighbours).

new NDP(privateKey, options)

Creates new NDP object

• privateKey - Key for message encoding/signing.
• options.refreshInterval - Interval in ms for refreshing (calling findNeighbours) the peer list (default: 60s).
• options.createSocket - A datagram (dgram) createSocket function, passed to Server (default: dgram.createSocket.bind(null, 'udp4')).
• options.timeout - Timeout in ms for server ping, passed to Server (default: 10s).
• options.endpoint - Endpoint information to send with the server ping, passed to Server (default: { address: '0.0.0.0', udpPort: null, tcpPort: null }).

ndp.bootstrap(peer) (async)

Uses a peer as new bootstrap peer and calls findNeighbouts.

• peer - Peer to be added, format { address: [ADDRESS], udpPort: [UDPPORT], tcpPort: [TCPPORT] }.

ndp.addPeer(object) (async)

Adds a new peer.

• object - Peer to be added, format { address: [ADDRESS], udpPort: [UDPPORT], tcpPort: [TCPPORT] }.

For other utility functions like getPeer, getPeers see ./src/ndp/index.js.

Events

Events emitted:

| Event | Description | | ------------- |:----------------------------------------:| | peer:added | Peer added to DHT bucket | | peer:removed | Peer removed from DHT bucket | | peer:new | New peer added | | listening | Forwarded from server | | close | Forwarded from server | | error | Forwarded from server |

RLP Transport Protocol

Connect to a peer, organize the communication, see ./src/rlp/

Usage

Create your RLP object:

const rlp = new devp2p.RLP(PRIVATE_KEY, {
  ndp: ndp,
  maxPeers: 25,
  capabilities: [
    devp2p.SEC.sec
  ],
  listenPort: null
})

API

RLP (extends EventEmitter)

Manages the handshake (ECIES) and the handling of the peer communication (Peer).

new RLPx(privateKey, options)

Creates new RLPx object

• privateKey - Key for message encoding/signing.
• options.timeout - Peer ping timeout in ms (default: 10s).
• options.maxPeers - Max number of peer connections (default: 10).
• options.clientId - Client ID string (default example: sec).
• options.remoteClientIdFilter - Optional list of client ID filter strings (e.g. ['sec']).
• options.capabilities - Upper layer protocol capabilities, e.g. [devp2p.SEC.sec].
• options.listenPort - The listening port for the server or null for default.
• options.ndp - NDP object for the peers to connect to (default: null, no NDP peer management).

rlp.connect(peer) (async)

Manually connect to peer without NDP.

• peer - Peer to connect to, format { id: PEER_ID, address: PEER_ADDRESS, port: PEER_PORT }.

For other connection/utility functions like listen, getPeers see ./src/rlp/index.js.

Events

Events emitted:

| Event | Description | | ------------- |:----------------------------------------:| | peer:added | Handshake with peer successful | | peer:removed | Disconnected from peer | | peer:error | Error connecting to peer | | listening | Forwarded from server | | close | Forwarded from server | | error | Forwarded from server |

SECBlock Wire Protocol (SEC)

Upper layer protocol for exchanging SECBlock network data like block headers or transactions with a node, see ./src/sec/.

Usage

Send the initial status message with sendStatus(), then wait for the corresponding status message to arrive to start the communication.

sec.once('status', () => {
  // Send an initial message
  sec.sendMessage()
})

Wait for follow-up messages to arrive, send your responses.

sec.on('message', async (code, payload) => {
  if (code === devp2p.SEC.MESSAGE_CODES.NEW_BLOCK_HASHES) {
    // Do something with your new block hashes :-)
  }
})

See the example.js example for a more detailed use case.

API

SEC (extends EventEmitter)

Handles the different message types like NEW_BLOCK_HASHES or GET_NODE_DATA (see MESSAGE_CODES) for a complete list. Currently protocol version PV is supported.

new SEC(privateKey, options)

Normally not instantiated directly but created as a SubProtocol in the Peer object.

• version - The protocol version for communicating, e.g. 1.
• peer - Peer object to communicate with.
• send - Wrapped peer.sendMessage() function where the communication is routed to.

sec.sendStatus(status)

Send initial status message.

• status - Status message to send, format { networkId: CHAIN_ID, td: TOTAL_DIFFICULTY_BUFFER, bestHash: BEST_HASH_BUFFER, genesisHash: GENESIS_HASH_BUFFER }.

sec.sendMessage(code, payload)

Send initial status message.

• code - The message code, see MESSAGE_CODES for available message types.
• payload - Payload as a list, will be rlp-encoded.

Events

Events emitted:

| Event | Description | | ------------- |:----------------------------------------:| | message | Message received | | status | Status info received |

Tests

There are unit tests in the test/ directory which can be run with:

npm run test

License

MIT