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devp2p

README.md

@ethereumjs/devp2p

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

  • Distributed Peer Table (DPT) / v4 Node Discovery / DNS Discovery
  • RLPx Transport Protocol
  • Ethereum Wire Protocol (ETH/65)
  • Light Ethereum Subprotocol (LES/2)

The library is based on ethereumjs/node-devp2p as well as other sub-libraries (node-* named) (all outdated).

Run/Build

To build the dist/ directory, run:

npm run build

You can also use ts-node to run a script without first transpiling to js (you need to npm i --save-dev ts-node first):

node -r ts-node/register [YOUR_SCRIPT_TO_RUN.ts]

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:

dpt.on('peer:added', (peer) => {
  // Do something...
})

Basic example to connect to some bootstrap nodes and get basic peer info:

Communicate with peers to read new transaction and block information:

Run an example with:

DEBUG=devp2p:* node -r ts-node/register ./examples/peer-communication.ts

Docs

For a complete API reference see the generated documentation.

Additionally you can find a description of the main entrypoints for using the different modules in the following sections.

Distributed Peer Table (DPT) / Node Discovery

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

Usage

Create your peer table:

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

Add some bootstrap nodes (or some custom nodes with dpt.addPeer()):

dpt.bootstrap(bootnode).catch((err) => console.error('Something went wrong!'))

API

See the following diagram for a high level overview on the library.

DPT (extends EventEmitter)

Distributed Peer Table. Manages a Kademlia DHT K-bucket (Kbucket) for storing peer information and a BanList for keeping a list of bad peers. Server implements the node discovery (ping, pong, findNeighbours).

new DPT(privateKey, options)

Creates new DPT object

  • privateKey - Key for message encoding/signing.
  • 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 }).
  • options.createSocket - A datagram (dgram) createSocket function, passed to Server (default: dgram.createSocket.bind(null, 'udp4')).
  • options.refreshInterval - Interval in ms for refreshing (calling findNeighbours) the peer list (default: 60s).
  • options.shouldFindNeighbours - Toggles whether or not peers should be queried with 'findNeighbours' to discover more peers (default: true)
  • options.shouldGetDnsPeers - Toggles whether or not peers should be discovered by querying EIP-1459 DNS lists (default: false)
  • options.dnsRefreshQuantity - Max number of candidate peers to retrieve from DNS records when attempting to discover new nodes (default: 25)
  • options.dnsNetworks - EIP-1459 ENR tree urls to query for peer discovery (default: network dependent)
  • options.dnsAddr - DNS server to query DNS TXT records from for peer discovery

dpt.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] }.

dpt.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/dpt/dpt.ts.

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

Reference

RLPx Transport Protocol

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

Usage

Instantiate an @ethereumjs/common instance with the network you want to connect to:

const common = new Common({ chain: Chain.Mainnet })

Create your RLPx object, e.g.:

const rlpx = new devp2p.RLPx(PRIVATE_KEY, {
  dpt,
  maxPeers: 25,
  capabilities: [devp2p.ETH.eth65, devp2p.ETH.eth64],
  common,
})

API

RLPx (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: ethereumjs-devp2p/v2.1.3/darwin-x64/nodejs).
  • options.remoteClientIdFilter - Optional list of client ID filter strings (e.g. ['go1.5', 'quorum']).
  • options.capabilities - Upper layer protocol capabilities, e.g. [devp2p.ETH.eth63, devp2p.ETH.eth62].
  • options.listenPort - The listening port for the server or null for default.
  • options.dpt - DPT object for the peers to connect to (default: null, no DPT peer management).
  • options.common - An instance of @ethereumjs/common.

rlpx.connect(peer) (async)

Manually connect to peer without DPT.

  • 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/rlpx/rlpx.ts.

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

Reference

Ethereum Wire Protocol (ETH)

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

Usage

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

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

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

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

See the peer-communication.ts example for a more detailed use case.

API

ETH (extends EventEmitter)

Handles the different message types like NEW_BLOCK_HASHES or GET_NODE_DATA (see MESSAGE_CODES) for a complete list.

new ETH(privateKey, options)

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

  • version - The protocol version for communicating, e.g. 65.
  • peer - Peer object to communicate with.
  • send - Wrapped peer.sendMessage() function where the communication is routed to.

eth.sendStatus(status)

Send initial status message.

  • status - Status message to send, format {td: TOTAL_DIFFICULTY_BUFFER, bestHash: BEST_HASH_BUFFER, genesisHash: GENESIS_HASH_BUFFER }, networkId (respectively chainId) is taken from the Common instance

eth.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

Reference

Light Ethereum Subprotocol (LES)

Upper layer protocol used by light clients, see ./src/les/.

Usage

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

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

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

les.on('message', async (code, payload) => {
  if (code === devp2p.LES.MESSAGE_CODES.BLOCK_HEADERS) {
    // Do something with your new block headers :-)
  }
})

See the peer-communication-les.ts example for a more detailed use case.

API

LES (extends EventEmitter)

Handles the different message types like BLOCK_HEADERS or GET_PROOFS_V2 (see MESSAGE_CODES) for a complete list. Currently protocol version LES/2 running in client-mode is supported.

new LES(privateKey, options)

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

  • version - The protocol version for communicating, e.g. 2.
  • peer - Peer object to communicate with.
  • send - Wrapped peer.sendMessage() function where the communication is routed to.

les.sendStatus(status)

Send initial status message.

  • status - Status message to send, format { headTd: TOTAL_DIFFICULTY_BUFFER, headHash: HEAD_HASH_BUFFER, headNum: HEAD_NUM_BUFFER, genesisHash: GENESIS_HASH_BUFFER }, networkId (respectively chainId) is taken from the Common instance

les.sendMessage(code, reqId, payload)

Send initial status message.

  • code - The message code, see MESSAGE_CODES for available message types.
  • reqId - Request ID, will be echoed back on response.
  • payload - Payload as a list, will be rlp-encoded.

Events

Events emitted:

Event Description
message Message received
status Status info received

Reference

Browser

While it's possible to bundle this package for the browser, some features do not work:

  • EIP-1459 (DNS Peer Discovery) is disabled due to the absence of a standard polyfill for Node's dns module. DNS discovery mode can be toggled on/off via the DPTOption shouldGetDnsPeers ("false" by default).

Tests

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

npm run test

Debugging

This library uses debug debugging utility package.

For the debugging output to show up, set the DEBUG environment variable (e.g. in Linux/Mac OS: export DEBUG=*,-babel).

Use the DEBUG environment variable to active the logger output you are interested in, e.g.:

DEBUG=devp2p:dpt:*,devp2p:eth node -r ts-node/register [YOUR_SCRIPT_TO_RUN.ts]

For more verbose output on logging (e.g. to output the entire msg payload) use the verbose logger in addition:

DEBUG=devp2p:dpt:*,devp2p:eth,verbose node -r ts-node/register [YOUR_SCRIPT_TO_RUN.ts]

Exemplary logging output:

Add peer: 52.3.158.184:30303 Geth/v1.7.3-unstable-479aa61f/linux-amd64/go1.9 (eth63) (total: 2)
  devp2p:rlpx:peer Received body 52.169.42.101:30303 01c110 +133ms
  devp2p:rlpx:peer Message code: 1 - 0 = 1 +0ms
  devp2p:rlpx refill connections.. queue size: 0, open slots: 20 +1ms
  devp2p:rlpx 52.169.42.101:30303 disconnect, reason: 16 +1ms
Remove peer: 52.169.42.101:30303 (peer disconnect, reason code: 16) (total: 1)

Developer

Diagram Updates

To update the structure diagram files in the root folder open the devp2p.drawio file in draw.io, make your changes, and open a PR with the updated files. Export svg and png with border width=20 and transparency=false. For png go to "Advanced" and select 300 DPI.

General References

Other Implementations

The following is a list of major implementations of the devp2p stack in other languages:

Links

License

MIT