Experimental Ark SmartBridge Listener

This is a proof-of-concept for an Ark Transaction SmartBridge listener.

How It Works

1. Consumer registers a message with the listener with a callback Url

2. Listener scans Ark network transactions for transactions containing your message token in the SmartBridge data field.

3. Listener sends matching transaction to registered consumer

Limitations

• The SmartBridge data field is very small, so we need to store the message payload externally and pass only the message token in Ark transactions.

• The SmartBridge Listener tokenizes messages in a centralized way. It would be nice to decentralize this using IPFS or some other distributed content network.

Explanation

The SmartBridge Listener scans Ark transactions for matching message tokens. When a matching message is found, it sends the transaction to the consumer for further processing.

In this example, we will create an "Ark Ethereum Contract Service" that allows a user to create an Ethereum contract using an Ark transaction.

This service will accept a block of Ethereum contract code and return a message token, destination Ark wallet, and required Ark amount.

The client will then send an Ark transaction of the required Ark amount to the destination wallet with the message token in the transaction Smartbridge field.

The Ark Transaction SmartBridge Listener will match the message token on the Ark transaction and forward the transaction information to the Ark Ethereum Contract Service, which will create an Ethereum contract with the matching message.

If the listener succeeds, it sends a return transaction to the client Ark wallet with any un-used balance and a message of success.

If the listener fails, it sends a return transaction to the client with the original amount less transaction fees.

Example

0. Set up environment dependencies

   The app requires ark-node to be running at on localhost:4000:

   app.js --genesis genesisBlock.testnet.json --config config.testnet.json
   

   This app also requires Ethereum RPC server to be running on localhost:8545:

   geth --dev --rpc --rpcapi 'web3,eth,debug' --rpccorsdomain="*"
   

   You can find server configurations in application.yml

1. Start the listener application (listens on localhost:8080)

   mvn spring-boot:run 
   

2. Create a Ethereum Contract Message

   The user will need to compile solidity contracts locally using solc compiler. This generates an abi and bin file needed to create the contract.

   solc --bin --abi --optimize -o data/solc-output/ data/sample.sol
   

   The user then creates a contract message with the contract data to the listener service:

   curl -X POST 'localhost:8080/contracts' \
       -F returnArkAddress=ARNJJruY6RcuYCXcwWsu4bx9kyZtntqeAx \
       -F abiJson=@data/solc-output/greeter.abi \
       -F code=@data/solc-output/greeter.bin \
       -F params=@data/sample-params.json \
       -F gasLimit=500000
   

   {
     "token" : "abe05cd7-40c2-4fb0-a4a7-8d2f76e74978",
     "createdAt" : "2017-07-04T21:59:38.129Z",
     "estimatedGasCost" : "214411",
     "estimatedArkCost" : "1.00000000",
     "serviceArkAddress": "AewU1vEmPrtQNjdVo33cX84bfovY3jNAkV", 
     "returnArkAddress" : "ARNJJruY6RcuYCXcwWsu4bx9kyZtntqeAx",
     "contractCode" : "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",
     "contractAbiJson" : "[{\"constant\":false,\"inputs\":[],\"name\":\"kill\",\"outputs\":[],\"payable\":false,\"type\":\"function\"},{\"constant\":true,\"inputs\":[],\"name\":\"greet\",\"outputs\":[{\"name\":\"\",\"type\":\"string\"}],\"payable\":false,\"type\":\"function\"},{\"inputs\":[{\"name\":\"_greeting\",\"type\":\"string\"}],\"payable\":false,\"type\":\"constructor\"}]",
     "contractParamsJson" : "[\"Hello World\"]"
   }
   

   The user must send an ark transaction to the serviceArkAddress with at least estimatedArkCost ark. Any un-used ark will be returned to returnArkAddress in a ark transaction created by the service.

3. Create an Ark Transaction

   Using the Ark javascript API, the user sends a transaction to the serviceArkAddress with the message token in the VendorField parameter. The listener service will match the ark transaction with the corresponding contract for processing.

   var serviceArkAddress = "AewU1vEmPrtQNjdVo33cX84bfovY3jNAkV";
   var messageToken = "abe05cd7-40c2-4fb0-a4a7-8d2f76e74978";
   var amount = 1.0000000;
   var transaction = ark.transaction.createTransaction(serviceArkAddress, amount, messageToken, "passphrase", "secondPassphrase");
   

4. Check the Status of Ethereum Contract Message

   curl -X GET 'localhost:8080/contracts/abe05cd7-40c2-4fb0-a4a7-8d2f76e74978'
   

   {
     "token" : "abe05cd7-40c2-4fb0-a4a7-8d2f76e74978",
     "createdAt" : "2017-07-04T21:59:38.129Z",
     "estimatedGasCost" : "214411.00",
     "estimatedArkCost" : "1.00",
     "serviceArkAddress": "AewU1vEmPrtQNjdVo33cX84bfovY3jNAkV", 
     "returnArkAddress" : "ARNJJruY6RcuYCXcwWsu4bx9kyZtntqeAx",
     "contractCode" : "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",
     "contractAbiJson" : "[{\"constant\":false,\"inputs\":[],\"name\":\"kill\",\"outputs\":[],\"payable\":false,\"type\":\"function\"},{\"constant\":true,\"inputs\":[],\"name\":\"greet\",\"outputs\":[{\"name\":\"\",\"type\":\"string\"}],\"payable\":false,\"type\":\"function\"},{\"inputs\":[{\"name\":\"_greeting\",\"type\":\"string\"}],\"payable\":false,\"type\":\"constructor\"}]",
     "contractParamsJson" : "[\"Hello World\"]"
     "actualArkCost": "0.80000000",
     "returnArkAmount": "0.2000000",
     "returnArkTransactionId": "49f55381c5c3c70f96d848df53ab7f9ae9881dbb8eb43e8f91f642018bf1258f",
     "contractTransactionHash": "500224999259823996",
     "contractAddress": "0xdaa24d02bad7e9d6a80106db164bad9399a0423e",
     "createdAt":"2017-07-01T22:35:57.695Z"
   }
   

5. Running the Ethereum Contract

   Load the generated Ethereum contract using the contract address in the eth console:

   geth --dev attach
   > var contractAddress = "0xdaa24d02bad7e9d6a80106db164bad9399a0423e"
   > var contractInfo = admin.getContractInfo(contractAddress)
   > var contract = eth.contract(contractInfo.info.abiDefinition);
   > var instance = contract.at(contractAddress);
   > instance.greet()
   "Hello World"