Ethereum sidechain

Introduction

The RPC API is conform to the Ethereum JSON RPC specs.

JSON-RPC Endpoint

Default JSON-RPC endpoints for a locally running node (launched with develap):

JSON-RPC support

The elastos-eth supports JSON-RPC 2.0, Batch requests, HTTP, IPC, WS.

About HEX value encoding

Currently there are two key datatypes that are passed over JSON: unformatted byte arrays and quantities. Both are passed with a hex encoding, however with different requirements to formatting:

When encoding QUANTITIES (integers, numbers): encode as hex, prefix with “0x”, the most compact representation (slight exception: zero should be represented as “0x0”). Examples:

  • 0x41 (65 in decimal)
  • 0x400 (1024 in decimal)
  • WRONG: 0x (should always have at least one digit - zero is “0x0”)
  • WRONG: 0x0400 (no leading zeroes allowed)
  • WRONG: ff (must be prefixed 0x)

When encoding UNFORMATTED DATA (byte arrays, account addresses, hashes, bytecode arrays): encode as hex, prefix with “0x”, two hex digits per byte. Examples:

  • 0x41 (size 1, “A”)
  • 0x004200 (size 3, “\0B\0”)
  • 0x (size 0, “”)
  • WRONG: 0xf0f0f (must be even number of digits)
  • WRONG: 004200 (must be prefixed 0x)

Commonly used API

The full Ethereum API reference can be found here. For a quick start, here are a few basic commands that can be used to make sure your Elastos ethereum sidechain runs well:

eth_gasPrice

Returns the current price per gas in wei.

Parameters

none

Returns

QUANTITY - A hex representation of the current gas price in wei.

Request example

curl -X POST -H 'Content-Type: application/json' -H 'Accept:application/json' --data '{"jsonrpc":"2.0","method":"eth_gasPrice","params":[],"id":73}' http://localhost:21636

Response example

{
  "id":73,
  "jsonrpc": "2.0",
  "result": "0x09184e72a000" // 10000000000000
}

eth_getBalance

Returns the ETH balance for the given address

Parameters

  1. DATA, 20 Bytes - address to check for balance.
  2. QUANTITY|TAG - integer block number, or the string "latest", "earliest" or "pending", see the default block parameter

Example Parameters

params: [
    '0xc94770007dda54cF92009BFF0dE90c06F603a09f',
    'latest'
]

Returns

QUANTITY - Current balance in wei.

Request example

curl -X POST -H 'Content-Type: application/json' -H 'Accept:application/json' --data '{"jsonrpc":"2.0","method":"eth_getBalance","params":["0xc94770007dda54cF92009BFF0dE90c06F603a09f", "latest"],"id":1}' http://localhost:21636

Response example

{
  "id":1,
  "jsonrpc": "2.0",
  "result": "0x0234c8a3397aab58" // 158972490234375000
}

eth_getBlockByHash

Returns information about a block from its hash.

Parameters

  1. DATA, 32 Bytes - Hash of a block.
  2. Boolean - If true it returns the full transaction objects, if false only the hashes of the transactions.

Example Parameters

params: [
   '0xe670ec64341771606e55d6b4ca35a1a6b75ee3d5145a99d05921026d1527331',
   true
]

Returns

Object - A block object, or null when no block was found:

  • number: QUANTITY - the block number. null when its pending block.
  • hash: DATA, 32 Bytes - hash of the block. null when its pending block.
  • parentHash: DATA, 32 Bytes - hash of the parent block.
  • nonce: DATA, 8 Bytes - hash of the generated proof-of-work. null when its pending block.
  • sha3Uncles: DATA, 32 Bytes - SHA3 of the uncles data in the block.
  • logsBloom: DATA, 256 Bytes - the bloom filter for the logs of the block. null when its pending block.
  • transactionsRoot: DATA, 32 Bytes - the root of the transaction trie of the block.
  • stateRoot: DATA, 32 Bytes - the root of the final state trie of the block.
  • receiptsRoot: DATA, 32 Bytes - the root of the receipts trie of the block.
  • miner: DATA, 20 Bytes - the address of the beneficiary to whom the mining rewards were given.
  • difficulty: QUANTITY - integer of the difficulty for this block.
  • totalDifficulty: QUANTITY - integer of the total difficulty of the chain until this block.
  • extraData: DATA - the “extra data” field of this block.
  • size: QUANTITY - integer the size of this block in bytes.
  • gasLimit: QUANTITY - the maximum gas allowed in this block.
  • gasUsed: QUANTITY - the total used gas by all transactions in this block.
  • timestamp: QUANTITY - the unix timestamp for when the block was collated.
  • transactions: Array - Array of transaction objects, or 32 Bytes transaction hashes depending on the last given parameter.
  • uncles: Array - Array of uncle hashes.

Request example

curl -X POST -H 'Content-Type: application/json' -H 'Accept:application/json' --data '{"jsonrpc":"2.0","method":"eth_getBlockByHash","params":["0xe670ec64341771606e55d6b4ca35a1a6b75ee3d5145a99d05921026d1527331", true],"id":1}' http://localhost:21636

Response example

{
    "id":1,
    "jsonrpc":"2.0",
    "result": {
    "number": "0x1b4", // 436
    "hash": "0xe670ec64341771606e55d6b4ca35a1a6b75ee3d5145a99d05921026d1527331",
    "parentHash": "0x9646252be9520f6e71339a8df9c55e4d7619deeb018d2a3f2d21fc165dde5eb5",
    "nonce": "0xe04d296d2460cfb8472af2c5fd05b5a214109c25688d3704aed5484f9a7792f2",
    "sha3Uncles": "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347",
    "logsBloom": "0xe670ec64341771606e55d6b4ca35a1a6b75ee3d5145a99d05921026d1527331",
    "transactionsRoot": "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
    "stateRoot": "0xd5855eb08b3387c0af375e9cdb6acfc05eb8f519e419b874b6ff2ffda7ed1dff",
    "miner": "0x4e65fda2159562a496f9f3522f89122a3088497a",
    "difficulty": "0x027f07", // 163591
    "totalDifficulty":  "0x027f07", // 163591
    "extraData": "0x0000000000000000000000000000000000000000000000000000000000000000",
    "size":  "0x027f07", // 163591
    "gasLimit": "0x9f759", // 653145
    "gasUsed": "0x9f759", // 653145
    "timestamp": "0x54e34e8e" // 1424182926
    "transactions": [{...},{ ... }] 
    "uncles": ["0x1606e5...", "0xd5145a9..."]
  }
}

Deprecated

@BPI make sure this is useless after using develap, as everything is already started. Move to the guides section if this still can be useful, but this is advanced

You can start the HTTP JSON-RPC with the –rpc flag

geth --rpc

change the default port (20636) and listing address (localhost) with:

geth --rpc --rpcaddr <ip> --rpcport <portnumber>

If accessing the RPC from a browser, CORS will need to be enabled with the appropriate domain set. Otherwise, JavaScript calls are limit by the same-origin policy and requests will fail:

geth --rpc --rpccorsdomain "http://localhost:3000"

The JSON RPC can also be started from the geth console using the admin.startRPC(addr, port) command.