《Nodejs开发加密货币》之八：一个精巧的p2p网络实现
来源：互联网 发布：c c 程序员面试指南 编辑：程序博客网 时间：2024/06/05 14:37
关于
《Nodejs开发加密货币》，是一个加密货币产品的详细开发文档，涉及到使用Nodejs开发产品的方方面面，从前端到后台、从服务器到客户端、从PC到移动、加密解密、区款链等各个环节。代码完全开源、文章免费分享。 相关资源见 http://ebookchain.org
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前言
加密货币都是去中心化的应用，去中心化的基础就是P2P网络，其作用和地位不言而喻，无可替代。
事实上，P2P网络不是什么新技术。但是，使用Nodejs开发的P2P网络，确实值得围观。这一篇，我们就来看看Ebookcoin的点对点网络是如何实现的。
源码
主要源码地址：
peer.js: https://github.com/Ebookcoin/ebookcoin/blob/master/modules/peer.js
transport.js: https://github.com/Ebookcoin/ebookcoin/blob/master/modules/transport.js
router.js: https://github.com/Ebookcoin/ebookcoin/blob/master/helpers/router.js
类图
流程图
解读
基于http的web应用，抓住路由的定义、设计与实现，是快速弄清业务逻辑的简单方法。目前，分析的是modules文件夹下的各个模块文件，这些模块基本都是独立的Express微应用，在开发和设计上相互独立，各不冲突，逻辑清晰，这为学习分析，提供了便利。
1.路由扩展
任何应用，只要提供Web访问能力或第三方访问的Api，都需要提供从地址到逻辑的请求分发功能，这就是路由。Ebookcoin是基于http协议的Express应用，Express底层基于Nodejs的connect模块，因此其路由设计简单而灵活。
前面，在入门部分，已经讲到对路由的分拆调用，这里是其简单实现。先看看helper/router.js吧。
<code class="hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;">// <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">27</span>行var Router = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> () { var router = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">require</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'express'</span>).Router(); router.use(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> (req, res, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">next</span>) { res.header(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Access-Control-Allow-Origin"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"*"</span>); res.header(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Access-Control-Allow-Headers"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Origin, X-Requested-With, Content-Type, Accept"</span>); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">next</span>(); }); router.map = map; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> router;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul>这段代码定义了一个Express路由器Router，并扩展了两个功能：
- 允许任何客户端调用。其实，就是设置了跨域请求，选项
Access-Control-Allow-Origin设置为*，自然任何IP和端口的节点都可以访问和被访问。 - 添加了地址映射方法。该方法的主要内容如下：
<code class="hljs javascript has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 3行</span><span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-title" style="box-sizing: border-box;">map</span><span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(root, config)</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">var</span> router = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>; <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">Object</span>.keys(config).forEach(<span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(params)</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">var</span> route = params.split(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">" "</span>); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (route.length != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span> || [<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"post"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"get"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"put"</span>].indexOf(route[<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>]) == -<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">Error</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"wrong map config"</span>); } router[route[<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>]](route[<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>], <span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(req, res, next)</span> {</span> root[config[params]]({<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"body"</span>: route[<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>] == <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"get"</span> ? req.query : req.body}, <span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(err, response)</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (err) { res.json({<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"success"</span>: <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">false</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"error"</span>: err}); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> res.json(extend({}, {<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"success"</span>: <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">true</span>}, response)); } }); }); });}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li></ul>该方法，接受两个对象作为参数：
- root: 定义了所要开放Api的逻辑函数;
- config: 定义了路由和root定义的函数的对应关系。
其运行的结果，就相当于：
<code class="hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;">router.get(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'/peers'</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span>(req, res, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">next</span>){ root.getPeers(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span>);})</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>这里关键的小技巧是，在js代码中，对象也是hash值，root.getPeers() 与 root‘getPeers’ 是一致的。不过后者可以用字符串变量代替，更加灵活，有点像ruby里的元编程。这是脚本语言的优势（简单的字符串拼接处理）。
扩展一下，在类似sails的框架（基于express)里，很多都是可以使用类似config.json的文件直接配置的，包括路由。参考这个函数，很容易理解和实现。
2.节点路由
很轻松就能在peer.js里找到上述map方法的使用：
<code class="hljs php has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 3行</span>Router = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">require</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'../helpers/router.js'</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 25</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span>.attachApi = <span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">()</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">var</span> router = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Router(); router.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">use</span>(<span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(req, res, next)</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (modules) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> next(); res.status(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">500</span>).send({success: <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>, error: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Blockchain is loading"</span>}); }); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 34行</span> router.map(shared, { <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"get /"</span>: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"getPeers"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"get /version"</span>: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"version"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"get /get"</span>: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"getPeer"</span> }); router.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">use</span>(<span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(req, res)</span> {</span> res.status(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">500</span>).send({success: <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>, error: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"API endpoint not found"</span>}); }); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 44行</span> library.network.app.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">use</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'/api/peers'</span>, router); library.network.app.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">use</span>(<span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(err, req, res, next)</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!err) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> next(); library.logger.error(req.url, err.toString()); res.status(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">500</span>).send({success: <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>, error: err.toString()}); });};</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li></ul>上面代码的34行，可以直观想象到，会有类似/version的路由出现，44行是express应用，这里就是将定义好的路由放在/api/peers前缀之下，可以确信peer.js文件提供了下面3个公共Api地址：
http://ip:port/api/peers/
http://ip:port/api/peers/version
http://ip:port/api/peers/get
当然，是不是可以直接这么调用，要看具体对应的函数是否还有其他的参数要求，比如：/api/peers/get，按照restful的api设计原则，可以理解为是获得具体某个节点信息，那么总该给个id之类的限定条件吧。看源码：
<code class="hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;">// <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">455</span>行library.scheme.validate(query, { type: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"object"</span>, properties: { ip_str: { type: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"string"</span>, minLength: <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span> }, port: { type: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"integer"</span>, minimum: <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, maximum: <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">65535</span> } }, required: [<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'ip_str'</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'port'</span>] }, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> (err) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span> // <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">480</span>行 private.getByFilter({ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span> }); });</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li></ul>这里，在具体运行过程中，library就是app.js里传过来的scope，该参数包含的scheme代表了一个z_schema实例。
z_schema是一个第三方组件，具体请看参考链接。该组件提供了json数据格式验证功能。上述代码的意思是：对请求参数query进行验证，验证规则是：object类型，属性ip_str要求长度不小于1的字符串，属性port要求0~65535之间的整数，并且都不能空（必需）。
这就说明，我们应该这样请求http://ip:port/api/peers/get?ip_str=0.0.0.0&port=1234，不然会返回错误信息。回头看看getPeers方法的实现，没有required字段，对应可以直接访问http://ip:port/api/peers/。
看480行，上面的地址，都会调用private.getByFilter()，并由它从sqlite数据库里查询数据表peers。这里涉及到 dblite第三方组件 (请看参考链接)，对请求操作sqlite数据库进行了简单封装。
3.节点保存
大多数应用，读数据相对简单，难在写数据。上面的代码，都是get请求，可以查寻节点及其信息。我们自然会问，查询的信息从哪里来？初始的节点在哪里？节点变更了，怎么办？
（1）初始化节点
从现实角度考虑，在一个P2P网络中，一个孤立的节点，在没有其他任何节点信息的情况下，仅仅靠网络扫描去寻找其他节点，将是一件很难完成的事情，更别提高效和安全了。
因此，在运行软件之前，初始化一些节点供联网使用，是最简单直接的解决方案。这个在配置文件config.json里，有直接体现：
<code class="hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;">// config.json <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">15</span>行<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"peers"</span>: { <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"list"</span>: [], <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"blackList"</span>: [], <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"options"</span>: { <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"timeout"</span>: <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4000</span> }},<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>list的数据格式为：
<code class="hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;">[ { ip: <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.0</span><span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">.0</span><span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">.0</span>, port: <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">7000</span> }, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span>]</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul>当然，也可以在启动的时候，通过参数--peers 1.2.3.4:70001, 2.1.2.3:7002提供（代码见app.js47行）。
（2）写入节点
写入节点，就是持久化，或者保存到数据库，或者保存到某个文件。这里保存到sqlite3数据库里的peers表了，代码如下：
<code class="hljs php has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// peer.js 347行</span>Peer.prototype.onBlockchainReady = <span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">()</span> {</span> async.eachSeries(library.config.peers.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">list</span>, <span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(peer, cb)</span> {</span> library.dbLite.query(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"INSERT OR IGNORE INTO peers(ip, port, state, sharePort) VALUES($ip, $port, $state, $sharePort)"</span>, { ip: ip.toLong(peer.ip), port: peer.port, state: <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>, <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//初始状态为2，都是健康的节点</span> sharePort: Number(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>) }, cb); }, <span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(err)</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (err) { library.logger.error(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'onBlockchainReady'</span>, err); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span>.count(<span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(err, count)</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (count) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span>.updatePeerList(<span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(err)</span> {</span> err && library.logger.error(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'updatePeerList'</span>, err); library.bus.message(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'peerReady'</span>); }) library.logger.info(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'Peers ready, stored '</span> + count); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { library.logger.warn(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'Peers list is empty'</span>); } }); });}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li></ul>这段代码的意思是，当区块链（后面篇章分析）加载完毕的时候（触发事件），依次将配置的节点写入数据库，如果数据库已经存在相同的记录就忽略，然后更新节点列表，触发节点加载完毕事件。
这里对数据库Sqlite的插入操作，插入语句是library.dbLite.query("INSERT OR IGNORE INTO peers，有意思的是IGNORE操作字符串，是sqlite3支持的（见参考），当数据库有相同记录的时候，该记录被忽略，继续往下执行。
执行成功，就会调用library.bus.message('peerReady')，进而触发peerReady事件。该事件的功能就是：
（3）更新节点
事件onPeerReady函数，如下：
<code class="hljs php has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// peer.js 374行</span>Peer.prototype.onPeerReady = <span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">()</span> {</span> setImmediate(<span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-title" style="box-sizing: border-box;">nextUpdatePeerList</span><span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">()</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span>.updatePeerList(<span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(err)</span> {</span> err && library.logger.error(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'updatePeerList timer'</span>, err); setTimeout(nextUpdatePeerList, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">60</span> * <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1000</span>); }) }); setImmediate(<span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-title" style="box-sizing: border-box;">nextBanManager</span><span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">()</span> {</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span>.banManager(<span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(err)</span> {</span> err && library.logger.error(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'banManager timer'</span>, err); setTimeout(nextBanManager, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">65</span> * <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1000</span>) }); });}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul>两个setImmediate函数的调用，一个循环更新节点列表，一个循环更新节点状态。
第一个循环调用
看看第一个循环调用的函数updatePeerList，
<code class="hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;">private.updatePeerList = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> (cb) { // <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">53</span>行 modules.transport.getFromRandomPeer({ api: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'/list'</span>, method: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'GET'</span> }, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> (err, data) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span> library.scheme.validate(data.body, { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span> // <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">124</span>行 self.update(peer, cb); }); }, cb); }); });};</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul>看53行，我们知道，程序通过transport模块的.getFromRandomPeer方法，逐个随机的验证节点信息，并将其做删除和更新处理。如此一来，各种调用关系更加清晰，看流程图更加直观。.getFromRandomPeer的代码：
<code class="hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;">// transport.js <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">474</span>行Transport.prototype.getFromRandomPeer = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> (config, options, cb) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span> // <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">481</span>行 async.retry(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">20</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> (cb) { modules.peer.list(config, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> (err, peers) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!err && peers.length) { var peer = peers[<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>]; // <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">485</span>行 self.getFromPeer(peer, options, cb); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> cb(err || <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"No peers in db"</span>); } }); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span>};</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li></ul>代码很简单，重要的是理解async.retry的用法（下篇技术分享，详细学习），该方法就是要重复调用第一个task函数20次，有正确返回结果就传给回调函数。这里，只要查到一个节点，就会传给485行的getFromPeer函数，该函数是检验处理现存节点的核心函数，代码如下：
<code class="hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;">// transport.js <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">500</span>行Transport.prototype.getFromPeer = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> (peer, options, cb) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span> var req = { // <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">519</span>行： 获得节点地址 url: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'http://'</span> + ip.fromLong(peer.ip) + <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">':'</span> + peer.port + url, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span> }; // <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">532</span>行： 使用`request`组件发送请求 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> request(req, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> (err, response, body) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (err || response.statusCode != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">200</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (peer) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (err && (err.code == <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"ETIMEDOUT"</span> || err.code == <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"ESOCKETTIMEDOUT"</span> || err.code == <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"ECONNREFUSED"</span>)) { // <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">542</span>行： 对于无法请求的，自然要删除 modules.peer.remove(peer.ip, peer.port, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> (err) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span> }); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!options.not_ban) { // <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">549</span>行： 对于状态码不是<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">200</span>的，比如<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">304</span>等禁止状态，就要更改其状态 modules.peer.state(peer.ip, peer.port, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">600</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> (err) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span> }); } } } cb && cb(err || (<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'request status code'</span> + response.statusCode)); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (port > <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span> && port <= <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">65535</span> && response.headers[<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'version'</span>] == library.config.version) { // <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">595</span>行： 一切问题都不存在 modules.peer.update({ ip: peer.ip, port: port, state: <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>, // <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">598</span>行： 看来健康的节点状态为<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span> });}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li></ul>这里最重要的是532行，request第三方组件的使用，请看参考链接。官方定义为简单的http客户端，功能足够强大，可以模拟浏览器访问信息，经常被用来做测试。
第二个循环调用
第二个循环调用的函数很简单，就是循环更改state和clock字段，主要是将禁止的状态state=0，修改为1，如下：
<code class="hljs javascript has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 142行</span>private.banManager = <span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">function</span> <span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(cb)</span> {</span> library.dbLite.query(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"UPDATE peers SET state = 1, clock = null where (state = 0 and clock - $now < 0)"</span>, {now: <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">Date</span>.now()}, cb);}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>综上，整个P2P网络的读写和更新都已经清楚，回头再看活动图和类图，就更加明朗了。
最后，补充一下数据库里，节点表格peers的字段信息：
<code class="hljs applescript has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-property" style="box-sizing: border-box;">id</span>,ip,port,state,os,sharePort,<span class="hljs-property" style="box-sizing: border-box;">version</span>,clock</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>
总结
本篇，重点阅读了peer.js文件，学习了一个使用Nodejs开发的P2P网络架构，其特点是：
- 产品提供初始节点列表，保障了初始化节点快速完成，不至于成为孤立节点;
- 节点具备跨域访问能力，任何节点之间都可以自由访问;
- 节点具备自我更新能力，定期查询和更新死掉的节点，保障网络始终畅通;
一旦达到一定的节点数量，就会形成一个互联互通的不死网络。搭建在这种网络上的服务，会充满怎样的诱惑？加密货币为什么会被认为是下一代互联网？这加起来不足千行的代码，可以给我们足够多的遐想空间。
这部分代码，涉及到dblite，request，z_schema等第三方组件，以及Ebookcoin自行实现的事件处理方法library.bus(在app.js文件的行)，都很简单，不再分享或赘述，请自行查阅。本篇涉及的代码中，关于回调的设计很多，值得总结和研究。async组件，被反复使用，有必须汇总一下，请关注后续的技术分享。
链接
本系列文章即时更新，若要掌握最新内容，请关注下面的链接
本源文地址： https://github.com/imfly/bitcoin-on-nodejs
电子书阅读： http://bitcoin-on-nodejs.ebookchain.org
参考
z_schema组件: https://github.com/Ebookcoin/z_schema
dblite组件： https://github.com/Ebookcoin/dblite
request组件： http://github.com/request/request
SQL As Understood By SQLite： https://www.sqlite.org/lang_conflict.html
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