A JavaScript implementation of ÐΞVp2p Protocol for SECBlock, Based on Ethereum

Usage no npm install needed!

<script type="module">
  import secBlockSecjsDevp2p from 'https://cdn.skypack.dev/@sec-block/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)


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]


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)


Create your peer table:

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


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: '', 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 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/


Create your RLP object:

const rlp = new devp2p.RLP(PRIVATE_KEY, {
  ndp: ndp,
  maxPeers: 25,
  capabilities: [
  listenPort: null


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 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/.


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

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.


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.


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 emitted:

Event Description
message Message received
status Status info received


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

npm run test