如何用JavaScript实现区块链?

Question

如何用JavaScript实现区块链

Answer 1

<span style="font-family:Arial, Helvetica, sans-serif;">'use strict';</span>var CryptoJS = require("crypto-js");var express = require("express");var bodyParser = require('body-parser');var WebSocket = require("ws");var http_port = process.env.HTTP_PORT || 3001;var p2p_port = process.env.P2P_PORT || 6001;var initialPeers = process.env.PEERS ? process.env.PEERS.split(',') : [];class Block { constructor(index, previousHash, timestamp, data, hash) { this.index = index; this.previousHash = previousHash.toString(); this.timestamp = timestamp; this.data = data; this.hash = hash.toString(); }}var sockets = [];var MessageType = { QUERY_LATEST: 0, QUERY_ALL: 1, RESPONSE_BLOCKCHAIN: 2};var getGenesisBlock = () => { return new Block(0, "0", 1465154705, "my genesis block!!", "816534932c2b7154836da6afc367695e6337db8a921823784c14378abed4f7d7");};var blockchain = [getGenesisBlock()];var initHttpServer = () => { var app = express(); app.use(bodyParser.json()); app.get('/blocks', (req, res) => res.send(JSON.stringify(blockchain))); app.post('/mineBlock', (req, res) => { var newBlock = generateNextBlock(req.body.data); addBlock(newBlock); broadcast(responseLatestMsg()); console.log('block added: ' + JSON.stringify(newBlock)); res.send(); }); app.get('/peers', (req, res) => { res.send(sockets.map(s => s._socket.remoteAddress + ':' + s._socket.remotePort)); }); app.post('/addPeer', (req, res) => { connectToPeers([req.body.peer]); res.send(); }); app.listen(http_port, () => console.log('Listening http on port: ' + http_port));};var initP2PServer = () => { var server = new WebSocket.Server({port: p2p_port}); server.on('connection', ws => initConnection(ws)); console.log('listening websocket p2p port on: ' + p2p_port);};var initConnection = (ws) => { sockets.push(ws); initMessageHandler(ws); initErrorHandler(ws); write(ws, queryChainLengthMsg());};var initMessageHandler = (ws) => { ws.on('message', (data) => { var message = JSON.parse(data); console.log('Received message' + JSON.stringify(message)); switch (message.type) { case MessageType.QUERY_LATEST: write(ws, responseLatestMsg()); break; case MessageType.QUERY_ALL: write(ws, responseChainMsg()); break; case MessageType.RESPONSE_BLOCKCHAIN: handleBlockchainResponse(message); break; } });};var initErrorHandler = (ws) => { var closeConnection = (ws) => { console.log('connection failed to peer: ' + ws.url); sockets.splice(sockets.indexOf(ws), 1); }; ws.on('close', () => closeConnection(ws)); ws.on('error', () => closeConnection(ws));};var generateNextBlock = (blockData) => { var previousBlock = getLatestBlock(); var nextIndex = previousBlock.index + 1; var nextTimestamp = new Date().getTime() / 1000; var nextHash = calculateHash(nextIndex, previousBlock.hash, nextTimestamp, blockData); return new Block(nextIndex, previousBlock.hash, nextTimestamp, blockData, nextHash);};var calculateHashForBlock = (block) => { return calculateHash(block.index, block.previousHash, block.timestamp, block.data);};var calculateHash = (index, previousHash, timestamp, data) => { return CryptoJS.SHA256(index + previousHash + timestamp + data).toString();};var addBlock = (newBlock) => { if (isValidNewBlock(newBlock, getLatestBlock())) { blockchain.push(newBlock); }};var isValidNewBlock = (newBlock, previousBlock) => { if (previousBlock.index + 1 !== newBlock.index) { console.log('invalid index'); return false; } else if (previousBlock.hash !== newBlock.previousHash) { console.log('invalid previoushash'); return false; } else if (calculateHashForBlock(newBlock) !== newBlock.hash) { console.log(typeof (newBlock.hash) + ' ' + typeof calculateHashForBlock(newBlock)); console.log('invalid hash: ' + calculateHashForBlock(newBlock) + ' ' + newBlock.hash); return false; } return true;};var connectToPeers = (newPeers) => { newPeers.forEach((peer) => { var ws = new WebSocket(peer); ws.on('open', () => initConnection(ws)); ws.on('error', () => { console.log('connection failed') }); });};var handleBlockchainResponse = (message) => { var receivedBlocks = JSON.parse(message.data).sort((b1, b2) => (b1.index - b2.index)); var latestBlockReceived = receivedBlocks[receivedBlocks.length - 1]; var latestBlockHeld = getLatestBlock(); if (latestBlockReceived.index > latestBlockHeld.index) { console.log('blockchain possibly behind. We got: ' + latestBlockHeld.index + ' Peer got: ' + latestBlockReceived.index); if (latestBlockHeld.hash === latestBlockReceived.previousHash) { console.log("We can append the received block to our chain"); blockchain.push(latestBlockReceived); broadcast(responseLatestMsg()); } else if (receivedBlocks.length === 1) { console.log("We have to query the chain from our peer"); broadcast(queryAllMsg()); } else { console.log("Received blockchain is longer than current blockchain"); replaceChain(receivedBlocks); } } else { console.log('received blockchain is not longer than received blockchain. Do nothing'); }};var replaceChain = (newBlocks) => { if (isValidChain(newBlocks) && newBlocks.length > blockchain.length) { console.log('Received blockchain is valid. Replacing current blockchain with received blockchain'); blockchain = newBlocks; broadcast(responseLatestMsg()); } else { console.log('Received blockchain invalid'); }};var isValidChain = (blockchainToValidate) => { if (JSON.stringify(blockchainToValidate[0]) !== JSON.stringify(getGenesisBlock())) { return false; } var tempBlocks = [blockchainToValidate[0]]; for (var i = 1; i < blockchainToValidate.length; i++) { if (isValidNewBlock(blockchainToValidate[i], tempBlocks[i - 1])) { tempBlocks.push(blockchainToValidate[i]); } else { return false; } } return true;};var getLatestBlock = () => blockchain[blockchain.length - 1];var queryChainLengthMsg = () => ({'type': MessageType.QUERY_LATEST});var queryAllMsg = () => ({'type': MessageType.QUERY_ALL});var responseChainMsg = () =>({ 'type': MessageType.RESPONSE_BLOCKCHAIN, 'data': JSON.stringify(blockchain)});var responseLatestMsg = () => ({ 'type': MessageType.RESPONSE_BLOCKCHAIN, 'data': JSON.stringify([getLatestBlock()])});var write = (ws, message) => ws.send(JSON.stringify(message));var broadcast = (message) => sockets.forEach(socket => write(socket, message));connectToPeers(initialPeers);initHttpServer();initP2PServer();