How to develop Decentralized App (ĐApp) on Ethereum
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Blockchain introduction Ethereum Đapp – General architecture Đapp – Environment development Đapp – Demo building Auction application
![Go Ethereum Client
Geth
ÐΞVp2p [TCP, 30303]
> JS API Console
IPC-RPC
WS-RPC [8546]
JSON-RPC [HTTP, 8545]
Disabled by default
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How to develop Decentralized App (ĐApp) on Ethereum
- 1. How to develop Decentralized App on Ethereum Feb-2018 Phi Huynh & Thien Nguyen
- 2. Follow us on https://facebook.com/devcafevn https://slideshare.com/devcafevn https://github.com/devcafevn
- 3. Agenda • Blockchain introduction • Ethereum • Đapp – General architecture • Đapp – Environment development • Đapp – Demo building Auction application
- 5. Hash • Arbitrary input • Same length output • Unlikely that two inputs share the same output
- 6. Blocks
- 7. Blockchain • Distributed (Everybody keep their own copy of the ledger) • Transaction immutability achieved by way of blocks & chaining • Leverages consensus mechanism for validating the transactions • Uses cryptography for trust, accountability, security • There is no single point of failure
- 9. Ethereum • A blockchain app platform that runs smart contracts
- 10. Go Ethereum Client Geth ÐΞVp2p [TCP, 30303] > JS API Console IPC-RPC WS-RPC [8546] JSON-RPC [HTTP, 8545] Disabled by default Disabled by default
- 11. Ethereum Network • Network Id = 1 • Morden: Network Id = 2 (retired) • Ropsten: Network Id = 3 • Rinkerby: Network Id = 4 • Kovan: Network Id = 42 • Network Id = Asigned Live Network Testnet Private Network
- 12. Demo Setup private Ethereum network
- 13. Setup private Ethereum network • Install geth https://geth.ethereum.org/downloads/ • Create genesis.json • Initialize geth node “$ geth init path/to/genesis.json” • Start geth • Attach to geth • JS console • Create account • Start mining https://github.com/devcafevn/ethereum-auction-app/tree/master/private-network
- 14. Using Ethereum Wallet and MetaMask Ethereum Wallet MetaMask You can install the MetaMask add-on in Chrome, Firefox, Opera https://github.com/ethereum/mist/releases
- 15. Ethereum account types • Has an address • Controlled by a private key • Has an address • No private key • Holds and run code External Owned Account Contract Account
- 16. Denominations Unit Wei Value Wei wei 1 wei 1 Kwei (babbage) 1e3 wei 1,000 Mwei (lovelace) 1e6 wei 1,000,000 Gwei (shannon) 1e9 wei 1,000,000,000 microether (szabo) 1e12 wei 1,000,000,000,000 milliether (finney) 1e15 wei 1,000,000,000,000,000 ether 1e18 wei 1,000,000,000,000,000,000
- 17. GAS • Gas is the unit in which EVM resource usage is measured • Gas limit (start gas): max amount of gas you willing to spend • Gas price: price of gas on ether you willing to pay. Miners decides the minimal acceptable price Transaction Fee = Gas used * Gas price Gas used < Gas limit => Refund Gas used > Gas limit => Out of gas exception, no change made
- 18. Dapp development
- 19. Remix • https://remix.ethereum.org • Writing your first smart contract pragma solidity ^0.4.0; contract MyAccount { uint private myBalance; function MyAccount(uint _myBalance) public{ myBalance = _myBalance; } function getBalance() public constant returns(uint){ return myBalance; } function add(uint _amount) public returns(uint){ myBalance += _amount; return myBalance; } }
- 20. Dapp - general architecture Network
- 21. Dapp - General architecture 2 Network DB Server
- 23. Online Auction App • Everyone can send their bids to a contract • The highest current bid is visible to every one • At the end of the bidding period - The highest bid is sent to the beneficiary - Other bidders can withdraw their bids Source code: https://github.com/devcafevn/ethereum-auction-app Image source: https://kryptomoney.com/italian-auction-house-now-accepting-payments- bitcoins/
- 24. Blockchain Landscape Big Picture Developer Tools Fin Tech File Storage Gaming Social Digital Asset Video Security And much much more … SMART CONTRACTS TOMO CHAIN
- 25. Blockchain – Innovation Journey When the journey began 2008 Adopting Tokenomics 2nd., beyond currency Inter organizational cooperation 3rd., Smart Contracts PoS, Scaling, on-chain, off-chain, … https://hbr.org/2017/02/a-brief-history-of-blockchain
- 26. Q & A Share to get more