@ethereumjs/devp2p

Introduction

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/66)
• Light Ethereum Subprotocol (LES/4)

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:

• simple

Communicate with peers to read new transaction and block information:

• peer-communication

Run an example with:

DEBUG=ethjs,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

• Node discovery protocol
• RLPx - Node Discovery Protocol
• Kademlia Peer Selection

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

• RLPx: Cryptographic Network & Transport Protocol
• devp2p wire protocol

Ethereum Wire Protocol (ETH)

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

• Ethereum wire protocol

Light Ethereum Subprotocol (LES)

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

BigInt Support

Starting with v4 the usage of BN.js for big numbers has been removed from the library and replaced with the usage of the native JS BigInt data type (introduced in ES2020).

Please note that number-related API signatures have changed along with this version update and the minimal build target has been updated to ES2020.

Events

Events emitted:

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

Reference

• Light client protocol

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

Introduction

This library uses the debug debugging utility package.

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

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

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

The following loggers are available:

| Logger | Description | | --------------------- | ---------------------------------------------------------------------------------------- | | devp2p:dpt | General DPT peer discovery logging | | devp2p:dpt:server | DPT server communication (ping, pong, findNeighbour,... messages) | | devp2p:dpt:ban-list | DPT ban list | | devp2p:dns:dns | DNS discovery logging | | devp2p:rlpx | General RLPx debug logger | | devp2p:rlpx:peer | RLPx peer message exchange logging (PING, PONG, HELLO, DISCONNECT,... messages) | | devp2p:eth | ETH protocol message logging (STATUS, GET_BLOCK_HEADER, TRANSACTIONS,... messages) | | devp2p:les | LES protocol message logging (STATUS, GET_BLOCK_HEADER, GET_PROOFS,... messages) |

Debug Verbosity

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

DEBUG=ethjs,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)

Per-Message Debugging

The following loggers from above support per-message debugging:

| Logger | Usage | | ----------------------------- | ---------------------------------------------------------------------------------------------------- | | devp2p:eth | e.g. devp2p:eth:GET_BLOCK_HEADERS | | devp2p:les | e.g. devp2p:les:GET_PROOFS | | devp2p:rlpx:peer | e.g. devp2p:rlpx:peer:HELLO | | devp2p:rlpx:peer:DISCONNECT | e.g. devp2p:rlpx:peer:DISCONNECT:TOO_MANY_PEERS (special logger to filter on DISCONNECT reasons) | | devp2p:dpt:server | e.g. devp2p:dpt:server:findneighbours |

Available messages can be added to the logger base name to filter on a per message basis. See the following example to filter on two message names along ETH protocol debugging:

DEBUG=ethjs,devp2p:eth:GET_BLOCK_HEADERS,devp2p:eth:BLOCK_HEADERS -r ts-node/register [YOUR_SCRIPT_TO_RUN.ts]

Exemplary logging output:

devp2p:eth:GET_BLOCK_HEADERS Received GET_BLOCK_HEADERS message from 207.154.201.177:30303: d188659b37d8e321bc52c782198181c08080 +50ms
devp2p:eth:GET_BLOCK_HEADERS Send GET_BLOCK_HEADERS message to 159.65.72.121:30303: c81bc682ded8328080 +431ms
devp2p:eth:BLOCK_HEADERS Received BLOCK_HEADERS message from 159.65.72.121:30303: c21bc0 +417ms
devp2p:eth:GET_BLOCK_HEADERS Send GET_BLOCK_HEADERS message to 162.55.98.224:30303: c81dc682df0a328080 +339ms
devp2p:eth:BLOCK_HEADERS Received BLOCK_HEADERS message from 162.55.98.224:30303: f968dd1df968d9f90217a0af80dab03492dfc689936dc9ff272ed3743da1... +72ms

Per-Peer Debugging

There are the following ways to limit debug output to a certain peer:

Logging per IP

Log output can be limited to one or several certain IPs. This can be useful to follow on the message exchange with a certain remote peer (e.g. a bootstrap peer):

DEBUG=ethjs,devp2p:3.209.45.79 -r ts-node/register [YOUR_SCRIPT_TO_RUN.ts]

First Connected

Logging can be limited to the peer the first successful subprotocol (e.g. ETH) connection could be established:

DEBUG=ethjs,devp2p:FIRST_PEER -r ts-node/register [YOUR_SCRIPT_TO_RUN.ts]

This logger can be used in various practical scenarios if you want to concentrate on the message exchange with just one peer.

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:

• Python: pydevp2p
• Go: Go Ethereum
• Elixir: Exthereum

Links

• Blog article series on implementing Ethereum protocol stack

EthereumJS

See our organizational documentation for an introduction to EthereumJS as well as information on current standards and best practices. If you want to join for work or carry out improvements on the libraries, please review our contribution guidelines first.

License

MIT