hello-ether

Private Ethereum testnet to develop and test decentralized apps

Prerequisites

• Geth (go-ethereum)

brew tap ethereum/ethereum 
brew install ethereum

Create temp genesis block

geth --identity "MyTestNetNode" --nodiscover --networkid 1999 --datadir data  init genesis.json

Create Ether Account

geth account new --datadir data

Save the adress value!

Address: {eab0d85372b745b6bf4d0f4e9b1e5d52e09891af}

Delete all data

geth removedb --datadir data

Replace new account adress in genesis.json and run the init_genesis_block.sh again

geth --identity "MyTestNetNode" --nodiscover --networkid 1999 --datadir data  init genesis.json

Prefunding

geth --identity "MyTestNetNode" --datadir data --nodiscover --networkid 1999 console

Check you account funds

web3.fromWei(eth.getBalance(eth.accounts[0]), "ether")

Starting with contracts

Important: Make sure that you include --datadir data when running any local testnet geth command!

Example: geth attach --datadir data

Login

personal.unlockAccount(eth.coinbase, 'password', 0)

Go to greeter folder

npm i

npm build

Run

 node_modules/.bin/testrpc

Open a NEW terminal window (with the first one still open and running), and run node :

node

Web3 = require('web3') web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545")); web3.eth.accounts

Now you sould be able to run

node lib.js

You should see something like:

| => node lib.js
Contract transaction send: TransactionHash: 0x096954decd6bed2d4485b12946930a2d2944948622648e1a8401bb02f156bcf7 waiting to be mined...
Contract mined! Yay! Address: 0xd2d12b8e56d804d547b1dc1f5fca489867d2c038
Contract {
  _eth:

 ...

Take note if the contrat address = 0xd2d12b8e56d804d547b1dc1f5fca489867d2c038

Once contract has been mined you can return to the geth javascript console and create an instance of your contract, and call greet on it.

To do this you need two things:

• the contract's ABI
• the contract address

To get the contracts ABI run

node_modules/babel-cli/bin/babel.js printAbi.js --out-file transpiledPrintAbi.js --no-comments && node transpiledPrintAbi.js

var myContract = web3.eth.contract([{"constant":false,"inputs":[],"name":"kill","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"greet","outputs":[{"name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"inputs":[{"name":"_greeting","type":"string"}],"payable":false,"stateMutability":"nonpayable","type":"constructor"}]).at(0xd2d12b8e56d804d547b1dc1f5fca489867d2c038).greet()

var greeter2 = eth.contract([{constant:false,inputs:[],name:'kill',outputs:[],type:'function'},{constant:true,inputs:[],name:'greet',outputs:[{name:'',type:'string'}],type:'function'},{inputs:[{name:'_greeting',type:'string'}],type:'constructor'}]).at('0xd2d12b8e56d804d547b1dc1f5fca489867d2c038');

References

• https://medium.com/@WWWillems/how-to-set-up-a-private-ethereum-testnet-blockchain-using-geth-and-homebrew-1106a27e8e1e
• https://github.com/evbots/greeter_contract
• https://github.com/ethereum/go-ethereum/wiki/Contract-Tutorial