200行代码实现blockchain 区块链实例详解

这篇文章主要介绍了200行代码实现blockchain 区块链的相关知识，非常不错，具有参考借鉴价值，需要的朋友参考下吧

了解blockchain的概念很简单（区块链，交易链块）：它是分布式的（即不是放置在同一台机器上，不同的网络设备上的）数据库支持主办记录日益增长的名单。但是，这也是容易混淆blockchain与我们试图帮他解决了目标 - 在人们心中的那一刻，这个词是相当强烈的交易，合同或智能cryptocurrency的概念有关。

只有在这里blockchain - 是不是一回事比特币，并理解链块的基本知识比它似乎更容易，尤其是在，它是基于源代码的情况下。在本文中，我们提出了建立与在JavaScript中200行代码的简单模型。这个项目，我们称之为NaiveChain的源代码，可以在GitHub上找到。第1部分和第2部分：如果您需要刷上它的功能，使用我们的备忘单，我们将使用标准的ECMAScript 6。
块结构

第一步 - 确定应包含块的元素。为简单起见，我们只包括最必要的：先前块的指数（指数），时间标记（时间戳），数据（数据），散列和散列，要录制，以保持电路的结构完整性。

 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(); } }

散列单元

哈希块需要保持数据的完整性。在我们的例子，这适用于算法SHA-256。这种类型的散列是不相关的开采，因为在这种情况下，我们并没有用表现证明实施保护。

 var calculateHash = (index, previousHash, timestamp, data) => { return CryptoJS.SHA256(index + previousHash + timestamp + data).toString(); };

产生单元

要生成块，我们需要知道前一个块的哈希，使我们在结构已经确定了元素的其余部分。数据由最终用户提供。

 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); };

存储单元

使用blockchain 存储阵列。第一个块总是硬编码“创世纪块”。

 var getGenesisBlock = () => { return new Block(0, "0", 1465154705, "my genesis block!!", "816534932c2b7154836da6afc367695e6337db8a921823784c14378abed4f7d7"); }; var blockchain = [getGenesisBlock()];

确认块的完整性

我们必须始终能够确认单元或电路的完整性。尤其是当你从其他单位新的单位，必须决定是否接受它们。

 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; };

选择链最长的

在电路块的顺序必须被明确指定，但是在发生冲突的情况下（例如，两个节点同时在同一生成的块和相同数量），我们选择电路，其中包含的块的数量较多。

 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'); } };

消息到其它网络节点

该网站的一个组成部分 - 与其他节点的数据交换。下列规则用于维护网络同步：
当一个节点产生新的单元，它会报告给网络;
当本机连接到新的盛宴，他要求有关最后生成的块信息;
当一个节点正面临着一个块，其中有一个指标比他还大，他增加了一个块到电路或请求的完整链条的信息。
自动搜索同龄人不执行，所有环节都手动添加。

单元的控制

用户应该能够以某种方式控制节点，通过将HTTP服务器解决。当与节点相互作用有以下功能：
打印所有单元的列表;
创建用户生成内容的新单元;
打印列表，或添加的节日。
互动的最直接的方式 - 通过卷曲：

一个节点上的所有块＃名单

curl http://localhost:3001/blocks

架构

值得注意的是，该网站是指两个Web服务器：HTTP进行用户控制的装置和向所述的WebSocket HTTP来安装节点之间的P2P连接。

如下为js 200行代码

 'use strict'; 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  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();

总结

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