Whitepaper - Ethereum Classic With Cover

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Ethereum Classic Documentation, Release 0.1 miner.stop(); balance = web3.fromWei(eth.getBalance(primary), "ether"); After you create transactions, you can force process them with the following lines: miner.start(1); admin.sleepBlocks(1); miner.stop(); You can check your pending transactions with: // shows transaction pool txpool.status // number of pending txs eth.getBlockTransactionCount("pending"); // print all pending txs eth.getBlock("pending", true).transactions If you submitted contract creation transaction, you can check if the desired code actually got inserted in the current blockchain: txhash = eth.sendTansaction({from:primary, data: code}) //... mining contractaddress = eth.getTransactionReceipt(txhash); eth.getCode(contractaddress) 1.7.3 Accessing Contracts and Transactions RPC In previous sections we have seen how contracts can be written, deployed and interacted with. Now it’s time to dive in the details of communicating with the Ethereum network and smart contracts. An Ethereum node offers a RPC interface. This interface gives Ðapp’s access to the Ethereum blockchain and functionality that the node provides, such as compiling smart contract code. It uses a subset of the JSON-RPC 2.0 specification (no support for notifications or named parameters) as serialisation protocol and is available over HTTP and IPC (unix domain sockets on linux/OSX and named pipe’s on Windows). If you are not interested in the details but are looking for an easy to use javascript library you can skip the following sections and continue with Using Web3. Conventions The RPC interface uses a couple of conventions that are not part of the JSON-RPC 2.0 specification: • Numbers are hex encoded. This decision was made because some languages have no or limited support for working with extremly large numbers. To prevent these type of errors numbers are hex encoded and it is up to the deverloper to parse these numbers and handle them appropriately. See the hex encoding section on the wiki for examples. • Default block number, several RPC methods accept a block number. In some cases it’s not possible to give a block number or not very convenient. For these cases the default block number can be one of these strings [”earliest”, “latest”, “pending”]. See the wiki page for a list of RPC methods that use the default block parameters. Deploy contract We will go through the different steps to deploy the following contract using only the RPC interface. 1.7. Contracts and Transactions 85
Ethereum Classic Documentation, Release 0.1 contract Multiply7 { event Print(uint); function multiply(uint input) returns (uint) { Print(input * 7); return input * 7; } } The first thing to do is make sure the HTTP RPC interface is enabled. This means for geth we supply the --rpc flag on startup and for eth the -j flag. In this example we use the geth node on a private development chain. Using this approach we don’t need ether on the real network. > geth --rpc --dev --mine --minerthreads 1 --unlock 0 console 2>>geth.log This will start the HTTP RPC interface on http://localhost:8545. Note: geth supports CORS, see the --rpccorsdomain flag for more information. We can verify that the interface is running by retrieving the coinbase address and balance using curl. Please note that data in these examples will differ on your local node. If you want to try these command replace the request params accordingly. > curl --data '{"jsonrpc":"2.0","method":"eth_coinbase", "id":1}' localhost:8545 {"id":1,"jsonrpc":"2.0","result":["0xeb85a5557e5bdc18ee1934a89d8bb402398ee26a"]} > curl --data '{"jsonrpc":"2.0","method":"eth_getBalance", "params": ["0xeb85a5557e5bdc18ee1934a89 {"id":2,"jsonrpc":"2.0","result":"0x1639e49bba16280000"} Remember when we said that numbers are hex encoded? In this case the balance is returned in Wei as a hex string. If we want to have the balance in Ether as a number we can use web3 from the geth console. > web3.fromWei("0x1639e49bba16280000", "ether") "410" Now that we have some ether on our private development chain we can deploy the contract. The first step is to verify that the solidity compiler is available. We can retrieve available compilers using the eth_getCompilers RPC method. > curl --data '{"jsonrpc":"2.0","method": "eth_getCompilers", "id": 3}' localhost:8545 {"id":3,"jsonrpc":"2.0","result":["Solidity"]} We can see that the solidity compiler is available. If it’s not available follow these instructions. The next step is to compile the Multiply7 contract to byte code that can be send to the EVM. > curl --data '{"jsonrpc":"2.0","method": "eth_compileSolidity", "params": ["contract Multiply7 { {"id":4,"jsonrpc":"2.0","result":{"Multiply7":{"code":"0x6060604052605f8060106000396000f3606060405 Now that we have the compiled code we need to determine how much gas it costs to deploy it. The RPC interface has an eth_estimateGas method that will give us an estimate. > curl --data '{"jsonrpc":"2.0","method": "eth_estimateGas", "params": [{"from": "0xeb85a5557e5bdc {"id":5,"jsonrpc":"2.0","result":"0xb8a9"} And finally deploy the contract. > curl --data '{"jsonrpc":"2.0","method": "eth_sendTransaction", "params": [{"from": "0xeb85a5557e {"id":6,"jsonrpc":"2.0","result":"0x3a90b5face52c4c5f30d507ccf51b0209ca628c6824d0532bcd6283df7c08a The transaction is accepted by the node and a transaction hash is returned. We can use this hash to track the transaction. The next step is to determine the address where our contract is deployed. Each executed transaction will create a receipt. This receipt contains various information about the transaction such as in which block the transaction 86 Chapter 1. Contents
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