Ethereumex

Elixir JSON-RPC client for the Ethereum blockchain

Installation

Add Ethereumex to your mix.exs dependencies:

Add ethereumex to your list of dependencies in mix.exs:

def deps do
  [{:ethereumex, "~> 0.3.2"}]
end

Ensure ethereumex is started before your application:

def application do
  [applications: [:ethereumex]]
end

Configuration

In config/config.exs, add Ethereum protocol host params to your config file

config :ethereumex,
  url: "http://localhost:8545"

Usage

Available methods:

web3_clientVersion
web3_sha3
net_version
net_peerCount
net_listening
eth_protocolVersion
eth_syncing
eth_coinbase
eth_mining
eth_hashrate
eth_gasPrice
eth_accounts
eth_blockNumber
eth_getBalance
eth_getStorageAt
eth_getTransactionCount
eth_getBlockTransactionCountByHash
eth_getBlockTransactionCountByNumber
eth_getUncleCountByBlockHash
eth_getUncleCountByBlockNumber
eth_getCode
eth_sign
eth_sendTransaction
eth_sendRawTransaction
eth_call
eth_estimateGas
eth_getBlockByHash
eth_getBlockByNumber
eth_getTransactionByHash
eth_getTransactionByBlockHashAndIndex
eth_getTransactionByBlockNumberAndIndex
eth_getTransactionReceipt
eth_getUncleByBlockHashAndIndex
eth_getUncleByBlockNumberAndIndex
eth_getCompilers
eth_compileLLL
eth_compileSolidity
eth_compileSerpent
eth_newFilter
eth_newBlockFilter
eth_newPendingTransactionFilter
eth_uninstallFilter
eth_getFilterChanges
eth_getFilterLogs
eth_getLogs
eth_getWork
eth_submitWork
eth_submitHashrate
db_putString
db_getString
db_putHex
db_getHex
shh_post
shh_version
shh_newIdentity
shh_hasIdentity
shh_newGroup
shh_addToGroup
shh_newFilter
shh_uninstallFilter
shh_getFilterChanges
shh_getMessages

Examples

iex> Ethereumex.HttpClient.web3_client_version
{:ok, "Parity//v1.7.2-beta-9f47909-20170918/x86_64-macos/rustc1.19.0"}

iex> Ethereumex.HttpClient.web3_sha3("wrong_param")
{:error, %{"code" => -32602, "message" => "Invalid params: invalid format."}}

iex> Ethereumex.HttpClient.eth_get_balance("0x407d73d8a49eeb85d32cf465507dd71d507100c1")
{:ok, "0x0"}

Note that all method names are snakecases, so, for example, shh_getMessages method has corresponding Ethereumex.HttpClient.shh_get_messages/1 method. Signatures can be found in Ethereumex.Client.Behaviour. There are more examples in tests.

eth_call example - Read only smart contract calls

In order to call a smart contract using the JSON-RPC interface you need to properly hash the data attribute (this will need to include the contract method signature along with arguments if any). You can do this manually or use a hex package like (ABI)[https://github.com/exthereum/abi] to parse your smart contract interface or encode individual calls.

defp deps do
  [
    ...
    {:ethereumex, "~> 0.3.2"},
    {:abi, "~> 0.1.8"}
    ...
  ]
end

Now load the abi and pass the method signature. Note that the address needs to be converted to bytes

address           = "0x123" |> String.slice(2..-1) |> Base.decode16(case: :mixed)
contract_address  = "0x432"  
abi_encoded_data  = ABI.encode("balanceOf(address)", [address])

Now you can use eth_call to execute this smart contract command:

balance_bytes = Ethereumex.HttpClient.eth_call(%{
  data: "0x" <> abi_encoded_data,
  contract: contract_address
})

To convert the balance into an integer:

balance_bytes
|> String.slice(2..-1)
|> Base.decode16!(case: :lower)
|> TypeDecoder.decode_raw([{:uint, 256}])
|> List.first

eth_send_raw_transaction example - Payable smart contract call

Calling a smart contract method that requires computation will cost you gas or ether (if that method requires payment also). This means you will have to sign your transactions using the private key that owns some ethereum. In order to send signed transactions you will need both (ABI)[https://hex.pm/packages/abi] and (Blockchain)[https://hex.pm/packages/blockchain] hex packages.

abi_encoded_data = ABI.encode("transferFrom(address,address,uint)", [from_address, to_address, token_id])
contrat_address = "0x123"

transaction_data = %Blockchain.Transaction{
    data: abi_encoded_data,
    gas_limit: 100_000,
    gas_price: 16_000_000_000,
    init: <<>>,
    nonce: 5,
    to: contract_address,
    value: 0
}
|> Blockchain.Transaction.Signature.sign_transaction(private_key)
|> Blockchain.Transaction.serialize()
|> ExRLP.encode()
|> Base.encode16(case: :lower)

Ethereumex.HttpClient.eth_send_raw_transaction("0x" <> transaction_data)

Custom requests

Many Ethereum protocol implementations support additional JSON-RPC API methods. To use them, you should call Ethereumex.HttpClient.request/3 method.

For example, let's call parity's personal_listAccounts method.

iex> Ethereumex.HttpClient.request("personal_listAccounts", [], [])
{:ok,
 ["0x71cf0b576a95c347078ec2339303d13024a26910",
  "0x7c12323a4fff6df1a25d38319d5692982f48ec2e"]}

Batch requests

To send batch requests use Ethereumex.HttpClient.batch_request/1 method.

requests = [
   {:web3_client_version, []},
   {:net_version, []},
   {:web3_sha3, ["0x68656c6c6f20776f726c64"]}
 ]
 Ethereumex.HttpClient.batch_request(requests)
 {
   :ok,
   [
     "Parity//v1.7.2-beta-9f47909-20170918/x86_64-macos/rustc1.19.0",
     "42",
     "0x47173285a8d7341e5e972fc677286384f802f8ef42a5ec5f03bbfa254cb01fad"
   ]
 }

Contributing

Fork it!
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request

Author

Ayrat Badykov (@ayrat555)

License

Ethereumex is released under the MIT License.

raininja / ethereumex