RNGeth implements a bridge between React Native and celo-blockchain (geth) in order to use the light client as part of React Native mobile applications.

• Android
• iOS

$ npm i react-native-geth --save

$ react-native link react-native-geth

import RNGeth, { NodeConfig } from 'react-native-geth';

// Network ID
const networkID = 1
// Chain ID
const chainID = 17
// genesis.json
const genesis = `{
  "config": {
    "chainId": ${chainID},
    "homesteadBlock": 0,
    "eip155Block": 0,
    "eip158Block": 0
  },
  "difficulty": "20",
  "gasLimit": "10000000",
  "alloc": {}
}`

const config: NodeConfig = {
  "bootnodeEnodes": [ // --bootnodesv5 / Enodes of v5 bootnodes for p2p discovery
    "enode://XXXX@X[::]:XXXX",
    "enode://YYYY@Y[::]:YYYY"
  ],
  "networkID": networkID, // --networkid / Network identifier (integer, 42220=mainnet, 62320=baklava (testnet), 44787=alfajores (testnet)) (default: 1)
  "maxPeers": 0, // --maxpeers / Maximum number of network peers (network disabled if set to 0) (default: 25)
  "genesis": genesis, // genesis.json file
  "nodeDir": ".celo", // --datadir / Data directory for the databases and keystore
  "keyStoreDir": "keystore", // --keystore / Directory for the keystore (default = inside the datadir)
  "enodes": "enode://XXXX@X[::]:XXXX" // static_nodes.json file. Comma separated enode URLs
  "noDiscovery": false, // --nodiscover / determines if the node will not participate in p2p discovery (v5)
  "syncMode": 5 // the number associated with a sync mode in `celo-blockchain/mobile/geth.go`
}

async function main() {
  const geth = new RNGeth()
  await geth.setConfig(config)
  const start = await geth.start()

  if (start) {
    console.log('Start :', start)
    const stop = await geth.stop()
    console.log('Stop :', stop)
  }
}

main())

• NodeConfig
• RNGeth
  • setConfig
  • start
  • stop
  • addAccount
  • listAccounts
  • unlockAccount
  • signTransaction
  • signTransactionPassphrase
  • signHash
  • signHashPassphrase

The object that holds the config of the node consists of these fields:

• bootnodeEnodes []string Enode URLs for P2P discovery bootstrap
• enodes string Comma separated enode URLs of static nodes
• genesis string genesis.json file
• keyStoreDir string Directory for the keystore (default = inside the datadir)
• logFile string Path where to write geth logfile
• logFileLogLevel number Log level when writing to file
• maxPeers number Maximum number of network peers (network disabled if set to 0) (default: 25)
• networkID number Network identifier
• noDiscovery boolean Determines if the node will not participate in p2p discovery (v5)
• nodeDir string Data directory for the databases and keystore
• syncMode number The number associated with a sync mode in celo-blockchain/mobile/geth.go
• useLightweightKDF boolean Enable Lightweight KDF

When dealing with blockchain accounts we're usually handling binary data in the hexadecimal format as a general convention of the ecosystem. These can be private keys, hashes, or transactions encoded in RLP format. The celo-blockchain (geth) library being more low-level expects byte arrays, but getting byte arrays accross the native bridge is troublesome. As mentioned above a hexadecimal encoded string is the common way of passing around such data but our native environments are lacking in standard library support for parsing hex strings. We could have added additional code for this, but it would increase our attack surface, it being hard(er) to test and maintain. Therefore, we've decided to rely on Base64 encoding which is better supported by the native platforms.

This means in several places where we're passing binary data to the bridge base64 is te preferred encoding. This is easily achieved on the javascript side with access to the Buffer type.

const base64String = Buffer.from(hexString, 'hex').toString('base64');

setConfig(config: NodeConfig): Promise

Configures the node and returns true on success, may throw errors.

start(): Promise

Start creates a live P2P node and starts running it. Returns true if a node was started, false if node was already running and may throw errors.

stop(): Promise

Terminates a running node along with all it's services. Returns true if a node was stopped, false if node was not running and may throw errors.

addAccount(privateKeyBase64: string, passphrase: string): Promise<address: string>

Adds an account based on the private key and a passphrase.

Parameters

• privateKeyBase64 string Private Key encoded in base64
• passphrase string Passphrase

Returns Promise return the address of the created account

unlockAccount(address: string, passphrase: string, timeout: number): Promise<address: string>

Unlock an account with a passphrase for a set duration.

Parameters

• address string The address of the account to unlock
• passphrase string The passphrase that unlocks the account
• timeout number The duration (in seconds) the account should remain unlocked

subscribeNewhead(): Promise

Subscribes to notifications about the current blockchain head, returns true if successful, may throw error.

listAccounts(): Promise<string[]>

Returns all account addresses managed by the key store.

signTransaction(txRLPBase64: string, signer: string): Promise<signedTxRLPBase64: string>

Sign a transaction with a previously unlocked account.

Parameters:

• txRLPBase64 - base64 encoded transaction in RLP format
• signer - the address of the signer (must be unlocked beforehand)

Returns the signed transaction in RLP format encoded as base64.

signTransactionPassphrase(txRLPBase64: string, signer: string, passphrase: string): Promise<signedTxRLPBase64: string>

Sign a transaction with a passphrase for the signer account.

Parameters:

• txRLPBase64 - base64 encoded transaction in RLP format
• signer - the address of the signer
• passphrase - the passphrase to unlock the signer account

Returns the signed transaction in RLP format encoded as base64.

signHash(hashBase64: string, signer: string): Promise<signatureBase64: string>

Sign a hash with a previously unlocked account.

Parameters:

• hashBase64 - base64 encoded hash
• signer - the address of the signer (must be unlocked beforehand)

Returns the signature (binary) encoded as base64.

signHashPassphrase(hashBase64: string, signer: string, passphrase: string): Promise<hashBase64: string>

Sign a hash with a passphrase for the signer account.

Parameters:

• hashBase64 - base64 encoded hash
• signer - the address of the signer
• passphrase - the passphrase to unlock the signer account

Returns the signature (binary) encoded as base64.

React Native Geth is released under the MIT license