如何用JavaScript实现区块链

2023-03-05 12:09:01JavaScript015

如何用JavaScript实现区块链,第1张

<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 || 3001var p2p_port = process.env.P2P_PORT || 6001var 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 = 1i <blockchainToValidate.lengthi++) {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()

《Node.js区块链开发》（朱志文）电子书网盘下载免费在线阅读

资源链接：

链接：https://pan.baidu.com/s/10Ts8Po9M563Sla4LwDEI-Q

提取码：z0rz

书名：Node.js区块链开发

作者：朱志文

豆瓣评分：4.8

出版社：机械工业出版社

出版年份：2017-5

内容简介：

开发人员。本书涉及前端、后台的方方面面，无论是前端开发人员，还是后台开发者都可以学习参考。

架构师。区块链本身是分布式、云计算的典范，本书详细描述了一款区块链产品的架构设计，他们可以通过本书学习掌握区块链是如何基于P2P网络构建复杂的自适应系统的。