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    49. 

  49. <html xmlns="http://www.w3.org/1999/xhtml" xmlns:wb="http://open.weibo.com/wb" >
    50. 

  50. 	<head>
    51. 

  51. 		<title>一步步搭建物联网系统(教你设计物联网系统)</title>
    52. 

  52. 		<meta name="keywords" content="设计物联网系统,物联网系统设计">
    53. 

  53. 		<meta name="description" content="一份关于如何设计物联网系统的文档">
    54. 

  54. 		<link rel="stylesheet" href="../css/vendor.css" />
    55. 

  55. 	</head>
    56. 

  56. 	<body class="container inner wrap">
    57. 

  57. 		<h1>一步步搭建物联网系统(教你设计物联网系统)</h1>
    58. 

  58. 	</body>
    59. 

  59. </html>
    60. 

  60. <div id="TOC">
    61. 

  61. <ul>
    62. 

  62. <li><a href="#restful的coap协议"><span class="toc-section-number">1</span> RESTful的CoAP协议</a><ul>
    63. 

  63. <li><a href="#coap-嵌入式系统的rest"><span class="toc-section-number">1.1</span> CoAP: 嵌入式系统的REST</a></li>
    64. 

  64. <li><a href="#coap-命令行工具"><span class="toc-section-number">1.2</span> CoAP 命令行工具</a><ul>
    65. 

  65. <li><a href="#node-coap-cli"><span class="toc-section-number">1.2.1</span> Node CoAP CLI</a></li>
    66. 

  66. <li><a href="#libcoap"><span class="toc-section-number">1.2.2</span> libcoap</a></li>
    67. 

  67. <li><a href="#firefox-copper"><span class="toc-section-number">1.2.3</span> Firefox Copper</a></li>
    68. 

  68. </ul></li>
    69. 

  69. <li><a href="#coap-helloworld"><span class="toc-section-number">1.3</span> CoAP Hello,World</a></li>
    70. 

  70. <li><a href="#coap-数据库查询"><span class="toc-section-number">1.4</span> CoAP 数据库查询</a><ul>
    71. 

  71. <li><a href="#node-module"><span class="toc-section-number">1.4.1</span> Node Module</a></li>
    72. 

  72. <li><a href="#node-sqlite3"><span class="toc-section-number">1.4.2</span> Node-Sqlite3</a></li>
    73. 

  73. <li><a href="#查询数据"><span class="toc-section-number">1.4.3</span> 查询数据</a></li>
    74. 

  74. </ul></li>
    75. 

  75. <li><a href="#coap-block"><span class="toc-section-number">1.5</span> CoAP Block</a><ul>
    76. 

  76. <li><a href="#coap-post"><span class="toc-section-number">1.5.1</span> CoAP POST</a></li>
    77. 

  77. <li><a href="#coap-content-types"><span class="toc-section-number">1.5.2</span> CoAP Content Types</a></li>
    78. 

  78. </ul></li>
    79. 

  79. <li><a href="#coap-json"><span class="toc-section-number">1.6</span> CoAP JSON</a></li>
    80. 

  80. </ul></li>
    81. 

  81. </ul>
    82. 

  82. </div>
    83. 

  83. <h1 id="restful的coap协议"><span class="header-section-number">1</span> RESTful的CoAP协议</h1>
    84. 

  84. <h2 id="coap-嵌入式系统的rest"><span class="header-section-number">1.1</span> CoAP: 嵌入式系统的REST</h2>
    85. 

  85. <p>引自维基百科上的介绍，用的是谷歌翻译。。。</p>
    86. 

  86. <blockquote>
    87. 

  87. <p>受约束的应用协议（COAP）是一种软件协议旨在以非常简单的电子设备，使他们能够在互联网上进行交互式通信中使用。它特别针对小型低功率传感器，开关，阀门和需要被控制或监督远程，通过标准的Internet网络类似的组件。 COAP是一个应用层协议，该协议是用于在资源受限的网络连接设备，例如无线传感器网络节点使用。 COAP被设计为容易地转换为HTTP与Web简化集成，同时也能满足特殊的要求，例如多播支持，非常低的开销，和简单性。多播，低开销，以及简单性是因特网极其重要物联网（IOT）和机器对机器（M2M）设备，这往往是积重难返，有太多的内存和电源，比传统的互联网设备有。因此，效率是非常重要的。 COAP可以在支持UDP或UDP的模拟大多数设备上运行。</p>
    88. 

  88. </blockquote>
    89. 

  89. <p>简单地来说，CoAP是简化了HTTP协议的RESTful API，因而也只提供了REST的四个方法，即PUT,GET,POST和DELETE。对于微小的资源受限，在资源受限的通信的IP的网络，HTTP不是一种可行的选择。它占用了太多的资源和太多的带宽。而对于物联网这种嵌入式设备来说，关于资源与带宽，是我们需要优先考虑的内容。</p>
    90. 

  90. <ul>
    91. 

  91. <li>CoAP采用了二进制报头，而不是文本报头(text header)</li>
    92. 

  92. <li>CoAP降低了头的可用选项的数量。</li>
    93. 

  93. <li>CoAP减少了一些HTTP的方法</li>
    94. 

  94. <li>CoAP可以支持检测装置</li>
    95. 

  95. </ul>
    96. 

  96. <h2 id="coap-命令行工具"><span class="header-section-number">1.2</span> CoAP 命令行工具</h2>
    97. 

  97. <p>为了测试测试我们的代码是否是正确工作，我们需要一个CoAP的命令行工具。目前有两个不错的工具可以使用。</p>
    98. 

  98. <ul>
    99. 

  99. <li>CoAP-cli，一个基于NodeJS的CoAP命令行工具，其核心是基于Node-CoAP库。</li>
    100. 

  100. <li>libcooap，一个用C写的CoAP命令行工具。</li>
    101. 

  101. <li>FireFox Copper， 一个Firefox的插件。</li>
    102. 

  102. </ul>
    103. 

  103. <h3 id="node-coap-cli"><span class="header-section-number">1.2.1</span> Node CoAP CLI</h3>
    104. 

  104. <p>安装命令如下</p>
    105. 

  105. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"> <span class="kw">npm</span> install coap-cli -g </code></pre></div>
    106. 

  106. <h4 id="coap命令行"><span class="header-section-number">1.2.1.1</span> CoAP命令行</h4>
    107. 

  107. <p>在coap-cli中，一共有四个方法。分别表示REST的四种不同的方式:</p>
    108. 

  108. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">Commands</span>:
    109. 

  109. 

  110. <span class="kw">get</span>                    performs a GET request
    111. 

  111. <span class="kw">put</span>                    performs a PUT request
    112. 

  112. <span class="kw">post</span>                   performs a POST request
    113. 

  113. <span class="kw">delete</span>                 performs a DELETE request</code></pre></div>
    114. 

  114. <p>在这里，我们用<a href="coap://vs0.inf.ethz.ch/" class="uri">coap://vs0.inf.ethz.ch/</a>来作一个简单的测试</p>
    115. 

  115. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">coap</span> get coap://vs0.inf.ethz.ch/
    116. 

  116. <span class="kw">(2.05)</span>  <span class="kw">************************************************************</span>
    117. 

  117. <span class="kw">I-D</span></code></pre></div>
    118. 

  118. <p>测试一下现在的最小的物联网系统CoAP版</p>
    119. 

  119. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">coap</span> get coap://iot-coap.phodal.com/id/1
    120. 

  120. <span class="kw">(2.05)</span>  [{<span class="st">&quot;id&quot;</span>:<span class="kw">1</span>,<span class="st">&quot;value&quot;</span>:<span class="st">&quot;is id 1&quot;</span>,<span class="st">&quot;sensors1&quot;</span>:19,<span class="st">&quot;sensors2&quot;</span>:20}]</code></pre></div>
    121. 

  121. <h3 id="libcoap"><span class="header-section-number">1.2.2</span> libcoap</h3>
    122. 

  122. <h4 id="mac-os-libcoap安装"><span class="header-section-number">1.2.2.1</span> mac os libcoap安装</h4>
    123. 

  123. <p>Mac OS下可以直接用</p>
    124. 

  124. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">brew</span> install libcoap</code></pre></div>
    125. 

  125. <h4 id="ubuntu-libcoap安装"><span class="header-section-number">1.2.2.2</span> Ubuntu libcoap安装</h4>
    126. 

  126. <p>Ubuntu GNU/Linux下</p>
    127. 

  127. <h4 id="windows-libcoap安装"><span class="header-section-number">1.2.2.3</span> Windows libcoap安装</h4>
    128. 

  128. <p>Windows 下</p>
    129. 

  129. <p>安装完libcoap，我们可以直接用自带的两个命令</p>
    130. 

  130. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">coap-client</span> 
    131. 

  131. <span class="kw">coap-server</span></code></pre></div>
    132. 

  132. <p>1.用coap-server启一个CoAP服务</p>
    133. 

  133. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">coap-server</span></code></pre></div>
    134. 

  134. <p>2.客户端获取数据</p>
    135. 

  135. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">coap-client</span> -m get coap://localhost</code></pre></div>
    136. 

  136. <p>返回结果</p>
    137. 

  137. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">v</span>:1 t:0 tkl:0 c:1 id:37109
    138. 

  138. <span class="kw">This</span> is a test server made with libcoap (see http://libcoap.sf.net) 
    139. 

  139. <span class="kw">Copyright</span> (C) <span class="kw">2010--2013</span> Olaf Bergmann <span class="kw">&lt;</span>bergmann@tzi.org<span class="kw">&gt;</span></code></pre></div>
    140. 

  140. <h3 id="firefox-copper"><span class="header-section-number">1.2.3</span> Firefox Copper</h3>
    141. 

  141. <p>为了能访问<a href="coap://localhost/" class="uri">coap://localhost/</a>，于是我们便需要安装一个Firefox并安装一个名为Copper的插件。</p>
    142. 

  142. <ol style="list-style-type: decimal">
    143. 

  143. <li><p>下载地址: <a href="https://addons.mozilla.org/en-US/firefox/addon/copper-270430/" class="uri">https://addons.mozilla.org/en-US/firefox/addon/copper-270430/</a></p></li>
    144. 

  144. <li><p>作为测试我们同样可以访问 <a href="coap://vs0.inf.ethz.ch:5683/" class="uri">coap://vs0.inf.ethz.ch:5683/</a></p></li>
    145. 

  145. </ol>
    146. 

  146. <h2 id="coap-helloworld"><span class="header-section-number">1.3</span> CoAP Hello,World</h2>
    147. 

  147. <p>接着我们便开始试试做一个简单的CoAP协议的应用:</p>
    148. 

  148. <p>这里用到的是一个Nodejs的扩展Node-CoAP</p>
    149. 

  149. <blockquote>
    150. 

  150. <p>node-coap is a client and server library for CoAP modelled after the http module.</p>
    151. 

  151. </blockquote>
    152. 

  152. <p>Node-CoAP是一个客户端和服务端的库用于CoAP的模块建模。创建一个package.json文件，添加这个库</p>
    153. 

  153. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="op">{</span>
    154. 

  154.   <span class="st">&quot;dependencies&quot;</span><span class="op">:{</span>
    155. 

  155.     <span class="st">&quot;coap&quot;</span><span class="op">:</span> <span class="st">&quot;0.7.2&quot;</span>
    156. 

  156.   <span class="op">}</span>
    157. 

  157. <span class="op">}</span></code></pre></div>
    158. 

  158. <p>接着执行</p>
    159. 

  159. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">npm</span> install</code></pre></div>
    160. 

  160. <p>就可以安装好这个库。如果遇到权限问题，请用</p>
    161. 

  161. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">sudo</span> npm install</code></pre></div>
    162. 

  162. <p>接着，创建这样一个app.js</p>
    163. 

  163. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="kw">const</span> coap        <span class="op">=</span> <span class="at">require</span>(<span class="st">&#39;coap&#39;</span>)
    164. 

  164.     <span class="op">,</span> server  <span class="op">=</span> <span class="va">coap</span>.<span class="at">createServer</span>()
    165. 

  165. 

  166. <span class="va">server</span>.<span class="at">on</span>(<span class="st">&#39;request&#39;</span><span class="op">,</span> <span class="kw">function</span>(req<span class="op">,</span> res) <span class="op">{</span>
    167. 

  167.   <span class="va">res</span>.<span class="at">end</span>(<span class="st">&#39;Hello &#39;</span> <span class="op">+</span> <span class="va">req</span>.<span class="va">url</span>.<span class="at">split</span>(<span class="st">&#39;/&#39;</span>)[<span class="dv">1</span>] <span class="op">+</span> <span class="st">&#39;</span><span class="sc">\n</span><span class="st">&#39;</span>)
    168. 

  168. <span class="op">}</span>)
    169. 

  169. 

  170. <span class="va">server</span>.<span class="at">listen</span>(<span class="kw">function</span>() <span class="op">{</span>
    171. 

  171.   <span class="va">console</span>.<span class="at">log</span>(<span class="st">&#39;server started&#39;</span>)
    172. 

  172. <span class="op">}</span>)  </code></pre></div>
    173. 

  173. <p>执行</p>
    174. 

  174. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">node</span> app.js</code></pre></div>
    175. 

  175. <p>便可以在浏览器上访问了，因为现在什么也没有，所以什么也不会返回。</p>
    176. 

  176. <p>接着下来再创建一个client端的js，并运行之</p>
    177. 

  177. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="kw">const</span> coap  <span class="op">=</span> <span class="at">require</span>(<span class="st">&#39;coap&#39;</span>) 
    178. 

  178.     <span class="op">,</span> req   <span class="op">=</span> <span class="va">coap</span>.<span class="at">request</span>(<span class="st">&#39;coap://localhost/World&#39;</span>)
    179. 

  179. 

  180. <span class="va">req</span>.<span class="at">on</span>(<span class="st">&#39;response&#39;</span><span class="op">,</span> <span class="kw">function</span>(res) <span class="op">{</span>
    181. 

  181.   <span class="va">res</span>.<span class="at">pipe</span>(<span class="va">process</span>.<span class="at">stdout</span>)
    182. 

  182. <span class="op">}</span>)
    183. 

  183. 

  184. <span class="va">req</span>.<span class="at">end</span>()</code></pre></div>
    185. 

  185. <p>就可以在console上输出</p>
    186. 

  186. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">Hello</span> World </code></pre></div>
    187. 

  187. <p>也就达到了我们的目的，用CoAP协议创建一个服务，接着我们应该用它创建更多的东西，如产生JSON数据，以及RESTful。和HTTP版的最小物联网系统一样，CoAP版的最小物联网系统也是要返回JSON的。</p>
    188. 

  188. <h2 id="coap-数据库查询"><span class="header-section-number">1.4</span> CoAP 数据库查询</h2>
    189. 

  189. <h3 id="node-module"><span class="header-section-number">1.4.1</span> Node Module</h3>
    190. 

  190. <p>这说里NodeJS Module的意义是因为我们需要在别的地方引用到db_helper这个库，也就是下一小节要的讲的内容。</p>
    191. 

  191. <p>这样我们就可以在server.js类似于这样去引用这个js库。</p>
    192. 

  192. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="kw">var</span> DBHelper <span class="op">=</span> <span class="at">require</span>(<span class="st">&#39;./db_helper.js&#39;</span>)<span class="op">;</span>
    193. 

  193. <span class="va">DBHelper</span>.<span class="at">initDB</span>()<span class="op">;</span></code></pre></div>
    194. 

  194. <p>而这样调用的前提是我们需要去声明这样的module，为了方便地导出函数功能调用。</p>
    195. 

  195. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="kw">function</span> <span class="at">DBHelper</span>()<span class="op">{</span>
    196. 

  196. <span class="op">}</span>
    197. 

  197. <span class="va">DBHelper</span>.<span class="at">initDB</span> <span class="op">=</span> <span class="kw">function</span>()<span class="op">{};</span>
    198. 

  198. <span class="va">module</span>.<span class="at">exports</span> <span class="op">=</span> DBHelper<span class="op">;</span></code></pre></div>
    199. 

  199. <h3 id="node-sqlite3"><span class="header-section-number">1.4.2</span> Node-Sqlite3</h3>
    200. 

  200. <p>这次我们用的是SQLite3(你可以用MySQL，出于安全考虑用SQLite3，SQLite3产生的是一个文件)。一个简单的initDB函数</p>
    201. 

  201. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="kw">var</span> db <span class="op">=</span> <span class="kw">new</span> <span class="va">sqlite3</span>.<span class="at">Database</span>(config[<span class="st">&quot;db_name&quot;</span>])<span class="op">;</span>
    202. 

  202. <span class="kw">var</span> create_table <span class="op">=</span> <span class="st">&#39;create table if not exists basic (&#39;</span> <span class="op">+</span> config[<span class="st">&quot;db_table&quot;</span>] <span class="op">+</span> <span class="st">&#39;);&#39;</span><span class="op">;</span>
    203. 

  203. 

  204. <span class="va">db</span>.<span class="at">serialize</span>(<span class="kw">function</span>() <span class="op">{</span>
    205. 

  205.     <span class="va">db</span>.<span class="at">run</span>(create_table)<span class="op">;</span>
    206. 

  206.     <span class="va">_</span>.<span class="at">each</span>(config[<span class="st">&quot;init_table&quot;</span>]<span class="op">,</span> <span class="kw">function</span>(insert_data) <span class="op">{</span>
    207. 

  207.         <span class="va">db</span>.<span class="at">run</span>(insert_data)<span class="op">;</span>
    208. 

  208.     <span class="op">}</span>)<span class="op">;</span>
    209. 

  209. <span class="op">}</span>)<span class="op">;</span>
    210. 

  210. <span class="va">db</span>.<span class="at">close</span>()<span class="op">;</span></code></pre></div>
    211. 

  211. <p>首先从配置中读取db_name，接着创建table，然后调用underscore的each方法，创建几个数据。配置如下所示</p>
    212. 

  212. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript">config <span class="op">=</span> <span class="op">{</span>
    213. 

  213.     <span class="st">&quot;db_name&quot;</span><span class="op">:</span> <span class="st">&quot;iot.db&quot;</span><span class="op">,</span>
    214. 

  214.     <span class="st">&quot;db_table&quot;</span><span class="op">:</span> <span class="st">&quot;id integer primary key, value text, sensors1 float, sensors2 float&quot;</span><span class="op">,</span>
    215. 

  215.     <span class="st">&quot;init_table&quot;</span><span class="op">:</span>[
    216. 

  216.         <span class="st">&quot;insert or replace into basic (id,value,sensors1,sensors2) VALUES (1, &#39;is id 1&#39;, 19, 20);&quot;</span><span class="op">,</span>
    217. 

  217.         <span class="st">&quot;insert or replace into basic (id,value,sensors1,sensors2) VALUES (2, &#39;is id 2&#39;, 20, 21);&quot;</span>
    218. 

  218.     ]<span class="op">,</span>
    219. 

  219.     <span class="st">&quot;query_table&quot;</span><span class="op">:</span><span class="st">&quot;select * from basic;&quot;</span>
    220. 

  220. <span class="op">};</span></code></pre></div>
    221. 

  221. <p>而之前所提到的url查询所做的事情便是</p>
    222. 

  222. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="va">DBHelper</span>.<span class="at">urlQueryData</span> <span class="op">=</span> <span class="kw">function</span> (url<span class="op">,</span> callback) <span class="op">{</span>
    223. 

  223.     <span class="kw">var</span> db <span class="op">=</span> <span class="kw">new</span> <span class="va">sqlite3</span>.<span class="at">Database</span>(<span class="st">&quot;iot.db&quot;</span>)<span class="op">;</span>
    224. 

  224.     <span class="kw">var</span> result <span class="op">=</span> []<span class="op">;</span>
    225. 

  225.     <span class="va">console</span>.<span class="at">log</span>(<span class="st">&quot;SELECT * FROM basic where &quot;</span> <span class="op">+</span> <span class="va">url</span>.<span class="at">split</span>(<span class="st">&#39;/&#39;</span>)[<span class="dv">1</span>] <span class="op">+</span> <span class="st">&quot;=&quot;</span> <span class="op">+</span> <span class="va">url</span>.<span class="at">split</span>(<span class="st">&#39;/&#39;</span>)[<span class="dv">2</span>])<span class="op">;</span>
    226. 

  226.     <span class="va">db</span>.<span class="at">all</span>(<span class="st">&quot;SELECT * FROM basic where &quot;</span> <span class="op">+</span> <span class="va">url</span>.<span class="at">split</span>(<span class="st">&#39;/&#39;</span>)[<span class="dv">1</span>] <span class="op">+</span> <span class="st">&quot;=&quot;</span> <span class="op">+</span> <span class="va">url</span>.<span class="at">split</span>(<span class="st">&#39;/&#39;</span>)[<span class="dv">2</span>]<span class="op">,</span> <span class="kw">function</span>(err<span class="op">,</span> rows) <span class="op">{</span>
    227. 

  227.         <span class="va">db</span>.<span class="at">close</span>()<span class="op">;</span>
    228. 

  228.         <span class="at">callback</span>(<span class="va">JSON</span>.<span class="at">stringify</span>(rows))<span class="op">;</span>
    229. 

  229.     <span class="op">}</span>)<span class="op">;</span>
    230. 

  230. <span class="op">};</span></code></pre></div>
    231. 

  231. <p>将URL传进来，便解析这个参数，接着再放到数据库中查询，再回调回结果。这样我们就可以构成之前所说的查询功能，而我们所谓的post功能似乎也可以用同样的方法加进去。</p>
    232. 

  232. <h3 id="查询数据"><span class="header-section-number">1.4.3</span> 查询数据</h3>
    233. 

  233. <p>简单地记录一下在IoT-CoAP中一次获取数据地过程。</p>
    234. 

  234. <p>先看看在示例中的Get.js的代码，这关乎在后面server端的代码。</p>
    235. 

  235. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="kw">const</span> coap       <span class="op">=</span> <span class="at">require</span>(<span class="st">&#39;coap&#39;</span>)
    236. 

  236.      <span class="op">,</span>requestURI <span class="op">=</span> <span class="st">&#39;coap://localhost/&#39;</span>
    237. 

  237.      <span class="op">,</span>url        <span class="op">=</span> <span class="at">require</span>(<span class="st">&#39;url&#39;</span>).<span class="at">parse</span>(requestURI <span class="op">+</span> <span class="st">&#39;id/1/&#39;</span>)
    238. 

  238.      <span class="op">,</span>req        <span class="op">=</span> <span class="va">coap</span>.<span class="at">request</span>(url)
    239. 

  239.      <span class="op">,</span>bl         <span class="op">=</span> <span class="at">require</span>(<span class="st">&#39;bl&#39;</span>)<span class="op">;</span>
    240. 

  240. 

  241. <span class="va">req</span>.<span class="at">setHeader</span>(<span class="st">&quot;Accept&quot;</span><span class="op">,</span> <span class="st">&quot;application/json&quot;</span>)<span class="op">;</span>
    242. 

  242. <span class="va">req</span>.<span class="at">on</span>(<span class="st">&#39;response&#39;</span><span class="op">,</span> <span class="kw">function</span>(res) <span class="op">{</span>
    243. 

  243.   <span class="va">res</span>.<span class="at">pipe</span>(<span class="at">bl</span>(<span class="kw">function</span>(err<span class="op">,</span> data) <span class="op">{</span>
    244. 

  244.     <span class="kw">var</span> json <span class="op">=</span> <span class="va">JSON</span>.<span class="at">parse</span>(data)<span class="op">;</span>
    245. 

  245.     <span class="va">console</span>.<span class="at">log</span>(json)<span class="op">;</span>
    246. 

  246.   <span class="op">}</span>))<span class="op">;</span>
    247. 

  247. 

  248. <span class="op">}</span>)<span class="op">;</span>
    249. 

  249. <span class="va">req</span>.<span class="at">end</span>()<span class="op">;</span></code></pre></div>
    250. 

  250. <p>const定义数据的方法，和我们在其他语言中有点像。只是这的const主要是为了程序的健壮型,减少程序出错，当然这不是javascript的用法。</p>
    251. 

  251. <p>我们构建了一个请求的URL</p>
    252. 

  252. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">coap</span>://localhost/id/1/</code></pre></div>
    253. 

  253. <p>我们对我们的请求添加了一个Header，内容是Accept，值是’application/json’也就是JSON格式。接着，便是等待请求回来，再处理返回的内容。</p>
    254. 

  254. <p><strong>判断请求的方法</strong></p>
    255. 

  255. <p>在这里先把一些无关的代码删除掉，并保证其能工作，so，下面就是简要的逻辑代码。</p>
    256. 

  256. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="kw">var</span> coap            <span class="op">=</span> <span class="at">require</span>(<span class="st">&#39;coap&#39;</span>)<span class="op">;</span>
    257. 

  257. <span class="kw">var</span> server          <span class="op">=</span> <span class="va">coap</span>.<span class="at">createServer</span>(<span class="op">{}</span>)<span class="op">;</span>
    258. 

  258. <span class="kw">var</span> request_handler <span class="op">=</span> <span class="at">require</span>(<span class="st">&#39;./request_handler.js&#39;</span>)<span class="op">;</span>
    259. 

  259. 

  260. <span class="va">server</span>.<span class="at">on</span>(<span class="st">&#39;request&#39;</span><span class="op">,</span> <span class="kw">function</span>(req<span class="op">,</span> res) <span class="op">{</span>
    261. 

  261.     <span class="cf">switch</span>(<span class="va">req</span>.<span class="at">method</span>)<span class="op">{</span>
    262. 

  262.         <span class="cf">case</span> <span class="st">&quot;GET&quot;</span><span class="op">:</span> <span class="va">request_handler</span>.<span class="at">getHandler</span>(req<span class="op">,</span> res)<span class="op">;</span>
    263. 

  263.             <span class="cf">break</span><span class="op">;</span>
    264. 

  264.     <span class="op">}</span>
    265. 

  265. <span class="op">}</span>)<span class="op">;</span>
    266. 

  266. 

  267. <span class="va">server</span>.<span class="at">listen</span>(<span class="kw">function</span>() <span class="op">{</span>
    268. 

  268.     <span class="va">console</span>.<span class="at">log</span>(<span class="st">&#39;server started&#39;</span>)<span class="op">;</span>
    269. 

  269. <span class="op">}</span>)<span class="op">;</span></code></pre></div>
    270. 

  270. <p>创建一个CoAP服务，判断req.method，也就是请求的方法，如果是GET的话，就调用request_handler.getHandler(req, res)。而在getHandler里，判断了下请求的Accept</p>
    271. 

  271. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="va">request_helper</span>.<span class="at">getHandler</span> <span class="op">=</span> <span class="kw">function</span>(req<span class="op">,</span> res) <span class="op">{</span>
    272. 

  272.     <span class="cf">switch</span> (<span class="va">req</span>.<span class="at">headers</span>[<span class="st">&#39;Accept&#39;</span>]) <span class="op">{</span>
    273. 

  273.         <span class="cf">case</span> <span class="st">&quot;application/json&quot;</span><span class="op">:</span>
    274. 

  274.             <span class="va">qh</span>.<span class="at">returnJSON</span>(req<span class="op">,</span> res)<span class="op">;</span>
    275. 

  275.             <span class="cf">break</span><span class="op">;</span>
    276. 

  276.         <span class="cf">case</span> <span class="st">&quot;application/xml&quot;</span><span class="op">:</span>
    277. 

  277.             <span class="va">qh</span>.<span class="at">returnXML</span>(req<span class="op">,</span> res)<span class="op">;</span>
    278. 

  278.             <span class="cf">break</span><span class="op">;</span>
    279. 

  279.     <span class="op">}</span>
    280. 

  280. <span class="op">};</span></code></pre></div>
    281. 

  281. <p>如果是json刚调用returnJSON,</p>
    282. 

  282. <p><strong>Database与回调</strong></p>
    283. 

  283. <p>而这里为了处理回调函数刚分为了两部分</p>
    284. 

  284. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="va">query_helper</span>.<span class="at">returnJSON</span> <span class="op">=</span> <span class="kw">function</span>(req<span class="op">,</span> res) <span class="op">{</span>
    285. 

  285.     <span class="va">DBHelper</span>.<span class="at">urlQueryData</span>(<span class="va">req</span>.<span class="at">url</span><span class="op">,</span> <span class="kw">function</span> (result) <span class="op">{</span>
    286. 

  286.         <span class="va">QueryData</span>.<span class="at">returnJSON</span>(result<span class="op">,</span> res)<span class="op">;</span>
    287. 

  287.     <span class="op">}</span>)<span class="op">;</span>
    288. 

  288. <span class="op">};</span></code></pre></div>
    289. 

  289. <p>而这里只是调用了</p>
    290. 

  290. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="va">DBHelper</span>.<span class="at">urlQueryData</span> <span class="op">=</span> <span class="kw">function</span> (url<span class="op">,</span> callback) <span class="op">{</span>
    291. 

  291.     <span class="kw">var</span> db <span class="op">=</span> <span class="kw">new</span> <span class="va">sqlite3</span>.<span class="at">Database</span>(config[<span class="st">&quot;db_name&quot;</span>])<span class="op">;</span>
    292. 

  292.     <span class="va">console</span>.<span class="at">log</span>(<span class="st">&quot;SELECT * FROM basic where &quot;</span> <span class="op">+</span> <span class="va">url</span>.<span class="at">split</span>(<span class="st">&#39;/&#39;</span>)[<span class="dv">1</span>] <span class="op">+</span> <span class="st">&quot;=&quot;</span> <span class="op">+</span> <span class="va">url</span>.<span class="at">split</span>(<span class="st">&#39;/&#39;</span>)[<span class="dv">2</span>])<span class="op">;</span>
    293. 

  293.     <span class="va">db</span>.<span class="at">all</span>(<span class="st">&quot;SELECT * FROM basic where &quot;</span> <span class="op">+</span> <span class="va">url</span>.<span class="at">split</span>(<span class="st">&#39;/&#39;</span>)[<span class="dv">1</span>] <span class="op">+</span> <span class="st">&quot;=&quot;</span> <span class="op">+</span> <span class="va">url</span>.<span class="at">split</span>(<span class="st">&#39;/&#39;</span>)[<span class="dv">2</span>]<span class="op">,</span> <span class="kw">function</span>(err<span class="op">,</span> rows) <span class="op">{</span>
    294. 

  294.         <span class="va">db</span>.<span class="at">close</span>()<span class="op">;</span>
    295. 

  295.         <span class="at">callback</span>(<span class="va">JSON</span>.<span class="at">stringify</span>(rows))<span class="op">;</span>
    296. 

  296.     <span class="op">}</span>)<span class="op">;</span>
    297. 

  297. <span class="op">};</span></code></pre></div>
    298. 

  298. <p>这里调用了node sqlite3去查询对应id的数据，用回调处理了数据无法到外部的问题，而上面的returnJSON则只是返回最后的结果，code以及其他的内容。</p>
    299. 

  299. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="va">QueryData</span>.<span class="at">returnJSON</span> <span class="op">=</span> <span class="kw">function</span>(result<span class="op">,</span> res) <span class="op">{</span>
    300. 

  300.     <span class="cf">if</span> (<span class="va">result</span>.<span class="at">length</span> <span class="op">==</span> <span class="dv">2</span>) <span class="op">{</span>
    301. 

  301.         <span class="va">res</span>.<span class="at">code</span> <span class="op">=</span> <span class="st">&#39;4.04&#39;</span><span class="op">;</span>
    302. 

  302.         <span class="va">res</span>.<span class="at">end</span>(<span class="va">JSON</span>.<span class="at">stringify</span>(<span class="op">{</span>
    303. 

  303.             <span class="dt">error</span><span class="op">:</span> <span class="st">&quot;Not Found&quot;</span>
    304. 

  304.         <span class="op">}</span>))<span class="op">;</span>
    305. 

  305.     <span class="op">}</span> <span class="cf">else</span> <span class="op">{</span>
    306. 

  306.         <span class="va">res</span>.<span class="at">code</span> <span class="op">=</span> <span class="st">&#39;2.05&#39;</span><span class="op">;</span>
    307. 

  307.         <span class="va">res</span>.<span class="at">end</span>(result)<span class="op">;</span>
    308. 

  308.     <span class="op">}</span>
    309. 

  309. <span class="op">};</span></code></pre></div>
    310. 

  310. <p>当resulst的结果为空时，返回一个404，因为没有数据。这样我们就构成了整个的链，再一步步返回结果。</p>
    311. 

  311. <p>在<a href="https://github.com/phodal/iot-coap">IoT-CoAP</a>中我们使用到了一个Block2的东西，于是便整理相关的一些资料，作一个简单的介绍，以及在代码中的使用。</p>
    312. 

  312. <h2 id="coap-block"><span class="header-section-number">1.5</span> CoAP Block</h2>
    313. 

  313. <p>CoAP是一个RESTful传输协议用于受限设备的节点和网络。基本的CoAP消息是一个不错的选择对于小型载荷如</p>
    314. 

  314. <ul>
    315. 

  315. <li>温度传感器</li>
    316. 

  316. <li>灯光开关</li>
    317. 

  317. <li>楼宇自动化设备</li>
    318. 

  318. </ul>
    319. 

  319. <p>然而，有时我们的应用需要传输更大的有效载荷，如——更新固件。与HTTP，TCP做繁重工作将大型有效载荷分成多个数据包，并确保他们所有到达并以正确的顺序被处理。</p>
    320. 

  320. <p>CoAP是同UDP与DLTS一样是基于数据报传输的，这限制了资源表示(resource representation)的最大大小，使得传输不需要太多的分割。虽然UDP支持通过IP分片传输更大的有效载荷，且仅限于64KiB，更重要的是，并没有真正很好地约束应用和网络。</p>
    321. 

  321. <p>而不是依赖于IP分片，这种规范基本COAP了对“块”选项，用于传输信息从多个资源区块的请求 - 响应对。在许多重要的情况下，阻止使服务器能够真正无状态：服务器可以处理每块分开传输，而无需建立连接以前的数据块传输的其他服务器端内存。</p>
    322. 

  322. <p>综上所述，块(Block)选项提供了传送一个最小的在分块的方式更大的陈述。</p>
    323. 

  323. <h3 id="coap-post"><span class="header-section-number">1.5.1</span> CoAP POST</h3>
    324. 

  324. <p>看看在IoT CoAP中的post示例。</p>
    325. 

  325. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="kw">const</span> coap     <span class="op">=</span> <span class="at">require</span>(<span class="st">&#39;coap&#39;</span>)
    326. 

  326.       <span class="op">,</span>request  <span class="op">=</span> <span class="va">coap</span>.<span class="at">request</span>
    327. 

  327.       <span class="op">,</span>bl       <span class="op">=</span> <span class="at">require</span>(<span class="st">&#39;bl&#39;</span>)
    328. 

  328.       <span class="op">,</span>req <span class="op">=</span> <span class="at">request</span>(<span class="op">{</span><span class="dt">hostname</span><span class="op">:</span> <span class="st">&#39;localhost&#39;</span><span class="op">,</span><span class="dt">port</span><span class="op">:</span><span class="dv">5683</span><span class="op">,</span><span class="dt">pathname</span><span class="op">:</span> <span class="st">&#39;&#39;</span><span class="op">,</span><span class="dt">method</span><span class="op">:</span> <span class="st">&#39;POST&#39;</span><span class="op">}</span>)<span class="op">;</span>
    329. 

  329. 

  330. <span class="va">req</span>.<span class="at">setOption</span>(<span class="st">&#39;Block2&#39;</span><span class="op">,</span>  [<span class="kw">new</span> <span class="at">Buffer</span>(<span class="st">&#39;1&#39;</span>)<span class="op">,</span><span class="kw">new</span> <span class="at">Buffer</span>(<span class="st">&quot;&#39;must&#39;&quot;</span>)<span class="op">,</span> <span class="kw">new</span> <span class="at">Buffer</span>(<span class="st">&#39;23&#39;</span>)<span class="op">,</span> <span class="kw">new</span> <span class="at">Buffer</span>(<span class="st">&#39;12&#39;</span>)])<span class="op">;</span>
    331. 

  331. <span class="va">req</span>.<span class="at">setHeader</span>(<span class="st">&quot;Accept&quot;</span><span class="op">,</span> <span class="st">&quot;application/json&quot;</span>)<span class="op">;</span>
    332. 

  332. <span class="va">req</span>.<span class="at">on</span>(<span class="st">&#39;response&#39;</span><span class="op">,</span> <span class="kw">function</span>(res) <span class="op">{</span>
    333. 

  333.     <span class="va">res</span>.<span class="at">pipe</span>(<span class="at">bl</span>(<span class="kw">function</span>(err<span class="op">,</span> data) <span class="op">{</span>
    334. 

  334.         <span class="va">console</span>.<span class="at">log</span>(data)<span class="op">;</span>
    335. 

  335.         <span class="va">process</span>.<span class="at">exit</span>(<span class="dv">0</span>)<span class="op">;</span>
    336. 

  336.     <span class="op">}</span>))<span class="op">;</span>
    337. 

  337. 

  338. <span class="op">}</span>)<span class="op">;</span>
    339. 

  339. 

  340. <span class="va">req</span>.<span class="at">end</span>()<span class="op">;</span></code></pre></div>
    341. 

  341. <p>Block2中一共有四个数据，相应的数据结果应该是</p>
    342. 

  342. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="op">{</span> <span class="dt">name</span><span class="op">:</span> <span class="st">&#39;Block2&#39;</span><span class="op">,</span> <span class="dt">value</span><span class="op">:</span> <span class="op">&lt;</span>Buffer <span class="dv">31</span><span class="op">&gt;</span> <span class="op">}</span>
    343. 

  343. <span class="op">{</span> <span class="dt">name</span><span class="op">:</span> <span class="st">&#39;Block2&#39;</span><span class="op">,</span> <span class="dt">value</span><span class="op">:</span> <span class="op">&lt;</span>Buffer <span class="dv">27</span> 6d <span class="dv">75</span> <span class="dv">73</span> <span class="dv">74</span> <span class="dv">27</span><span class="op">&gt;</span> <span class="op">}</span>
    344. 

  344. <span class="op">{</span> <span class="dt">name</span><span class="op">:</span> <span class="st">&#39;Block2&#39;</span><span class="op">,</span> <span class="dt">value</span><span class="op">:</span> <span class="op">&lt;</span>Buffer <span class="dv">32</span> <span class="dv">33</span><span class="op">&gt;</span> <span class="op">}</span>
    345. 

  345. <span class="op">{</span> <span class="dt">name</span><span class="op">:</span> <span class="st">&#39;Block2&#39;</span><span class="op">,</span> <span class="dt">value</span><span class="op">:</span> <span class="op">&lt;</span>Buffer <span class="dv">31</span> <span class="dv">32</span><span class="op">&gt;</span> <span class="op">}</span></code></pre></div>
    346. 

  346. <p>这是没有解析的Block2，简单地可以用</p>
    347. 

  347. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="va">_</span>.<span class="at">values</span>(e).<span class="at">toString</span>()</code></pre></div>
    348. 

  348. <p>将结果转换为</p>
    349. 

  349. <p>Block2,1 Block2,‘must’ Block2,23 Block2,12</p>
    350. 

  350. <p>接着按“,”分开，</p>
    351. 

  351. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="va">_</span>.<span class="at">values</span>(e).<span class="at">toString</span>().<span class="at">split</span>(<span class="st">&#39;,&#39;</span>)[<span class="dv">1</span>]</code></pre></div>
    352. 

  352. <p>就有</p>
    353. 

  353. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">[</span> <span class="st">&#39;1&#39;</span>, <span class="st">&#39;\&#39;</span>must<span class="dt">\&#39;</span><span class="st">&#39;, &#39;</span>23<span class="st">&#39;, &#39;</span>12<span class="st">&#39; ]</span></code></pre></div>
    354. 

  354. <p>便可以很愉快地将其post到数据库中了，</p>
    355. 

  355. <p>在做IoT-CoAP的过程中只支持JSON，查阅CoAP的草稿时发现支持了诸多的Content Types。</p>
    356. 

  356. <h3 id="coap-content-types"><span class="header-section-number">1.5.2</span> CoAP Content Types</h3>
    357. 

  357. <p>以下文字来自谷歌翻译:</p>
    358. 

  358. <blockquote>
    359. 

  359. <p>互联网媒体类型是通过HTTP字符串标识，如“application/xml”。该字符串是由一个顶层的类型“applicaion”和子类型的“XML”。为了尽量减少使用这些类型的媒体类型来表示的开销消息有效载荷，COAP定义一个标识符编码方案互联网媒体类型的子集。预计这桌将可扩展标识符的值的IANA维护。内容类型选项被格式化为一个8位无符号整数。初始映射到一个合适的互联网媒体类型标识符表所示。复合型高层次类型（multipart和不支持消息）。标识符值是从201-255保留的特定于供应商的，应用程序特定的或实验使用和不由IANA。</p>
    360. 

  360. </blockquote>
    361. 

  361. <p>下面是HTTP的标识符及类型</p>
    362. 

  362. <table>
    363. 

  363. <thead>
    364. 

  364. <tr class="header">
    365. 

  365. <th align="left">Internet media type</th>
    366. 

  366. <th align="left">Identifier</th>
    367. 

  367. </tr>
    368. 

  368. </thead>
    369. 

  369. <tbody>
    370. 

  370. <tr class="odd">
    371. 

  371. <td align="left">text/plain (UTF-8)</td>
    372. 

  372. <td align="left">0</td>
    373. 

  373. </tr>
    374. 

  374. <tr class="even">
    375. 

  375. <td align="left">text/xml (UTF-8)</td>
    376. 

  376. <td align="left">1</td>
    377. 

  377. </tr>
    378. 

  378. <tr class="odd">
    379. 

  379. <td align="left">text/csv (UTF-8)</td>
    380. 

  380. <td align="left">2</td>
    381. 

  381. </tr>
    382. 

  382. <tr class="even">
    383. 

  383. <td align="left">text/html (UTF-8)</td>
    384. 

  384. <td align="left">3</td>
    385. 

  385. </tr>
    386. 

  386. <tr class="odd">
    387. 

  387. <td align="left">image/gif</td>
    388. 

  388. <td align="left">21</td>
    389. 

  389. </tr>
    390. 

  390. <tr class="even">
    391. 

  391. <td align="left">image/jpeg</td>
    392. 

  392. <td align="left">22</td>
    393. 

  393. </tr>
    394. 

  394. <tr class="odd">
    395. 

  395. <td align="left">image/png</td>
    396. 

  396. <td align="left">23</td>
    397. 

  397. </tr>
    398. 

  398. <tr class="even">
    399. 

  399. <td align="left">image/tiff</td>
    400. 

  400. <td align="left">24</td>
    401. 

  401. </tr>
    402. 

  402. <tr class="odd">
    403. 

  403. <td align="left">audio/raw</td>
    404. 

  404. <td align="left">25</td>
    405. 

  405. </tr>
    406. 

  406. <tr class="even">
    407. 

  407. <td align="left">video/raw</td>
    408. 

  408. <td align="left">26</td>
    409. 

  409. </tr>
    410. 

  410. <tr class="odd">
    411. 

  411. <td align="left">application/link-format [I-D.ietf-core-link-format]</td>
    412. 

  412. <td align="left">40</td>
    413. 

  413. </tr>
    414. 

  414. <tr class="even">
    415. 

  415. <td align="left">application/xml</td>
    416. 

  416. <td align="left">41</td>
    417. 

  417. </tr>
    418. 

  418. <tr class="odd">
    419. 

  419. <td align="left">application/octet-stream</td>
    420. 

  420. <td align="left">42</td>
    421. 

  421. </tr>
    422. 

  422. <tr class="even">
    423. 

  423. <td align="left">application/rdf+xml</td>
    424. 

  424. <td align="left">43</td>
    425. 

  425. </tr>
    426. 

  426. <tr class="odd">
    427. 

  427. <td align="left">application/soap+xml</td>
    428. 

  428. <td align="left">44</td>
    429. 

  429. </tr>
    430. 

  430. <tr class="even">
    431. 

  431. <td align="left">application/atom+xml</td>
    432. 

  432. <td align="left">45</td>
    433. 

  433. </tr>
    434. 

  434. <tr class="odd">
    435. 

  435. <td align="left">application/xmpp+xml</td>
    436. 

  436. <td align="left">46</td>
    437. 

  437. </tr>
    438. 

  438. <tr class="even">
    439. 

  439. <td align="left">application/exi</td>
    440. 

  440. <td align="left">47</td>
    441. 

  441. </tr>
    442. 

  442. <tr class="odd">
    443. 

  443. <td align="left">application/x-bxml</td>
    444. 

  444. <td align="left">48</td>
    445. 

  445. </tr>
    446. 

  446. <tr class="even">
    447. 

  447. <td align="left">application/fastinfoset</td>
    448. 

  448. <td align="left">49</td>
    449. 

  449. </tr>
    450. 

  450. <tr class="odd">
    451. 

  451. <td align="left">application/soap+fastinfoset</td>
    452. 

  452. <td align="left">50</td>
    453. 

  453. </tr>
    454. 

  454. <tr class="even">
    455. 

  455. <td align="left">application/json</td>
    456. 

  456. <td align="left">51</td>
    457. 

  457. </tr>
    458. 

  458. </tbody>
    459. 

  459. </table>
    460. 

  460. <p>而在CoAP中只有简单地几个</p>
    461. 

  461. <table>
    462. 

  462. <thead>
    463. 

  463. <tr class="header">
    464. 

  464. <th align="left">Media type</th>
    465. 

  465. <th align="left">Encoding</th>
    466. 

  466. <th align="left">Id.</th>
    467. 

  467. <th align="left">Reference</th>
    468. 

  468. </tr>
    469. 

  469. </thead>
    470. 

  470. <tbody>
    471. 

  471. <tr class="odd">
    472. 

  472. <td align="left">text/plain;</td>
    473. 

  473. <td align="left">-</td>
    474. 

  474. <td align="left">0</td>
    475. 

  475. <td align="left">[RFC2046][RFC3676][RFC5147]</td>
    476. 

  476. </tr>
    477. 

  477. <tr class="even">
    478. 

  478. <td align="left">charset=utf-8</td>
    479. 

  479. <td align="left"></td>
    480. 

  480. <td align="left"></td>
    481. 

  481. <td align="left"></td>
    482. 

  482. </tr>
    483. 

  483. <tr class="odd">
    484. 

  484. <td align="left">application/</td>
    485. 

  485. <td align="left">-</td>
    486. 

  486. <td align="left">40</td>
    487. 

  487. <td align="left">[RFC6690]</td>
    488. 

  488. </tr>
    489. 

  489. <tr class="even">
    490. 

  490. <td align="left">link-format</td>
    491. 

  491. <td align="left"></td>
    492. 

  492. <td align="left"></td>
    493. 

  493. <td align="left"></td>
    494. 

  494. </tr>
    495. 

  495. <tr class="odd">
    496. 

  496. <td align="left">application/xml</td>
    497. 

  497. <td align="left">-</td>
    498. 

  498. <td align="left">41</td>
    499. 

  499. <td align="left">[RFC3023]</td>
    500. 

  500. </tr>
    501. 

  501. <tr class="even">
    502. 

  502. <td align="left">application/</td>
    503. 

  503. <td align="left">-</td>
    504. 

  504. <td align="left">42</td>
    505. 

  505. <td align="left">[RFC2045][RFC2046]</td>
    506. 

  506. </tr>
    507. 

  507. <tr class="odd">
    508. 

  508. <td align="left">octet-stream</td>
    509. 

  509. <td align="left"></td>
    510. 

  510. <td align="left"></td>
    511. 

  511. <td align="left"></td>
    512. 

  512. </tr>
    513. 

  513. <tr class="even">
    514. 

  514. <td align="left">application/exi</td>
    515. 

  515. <td align="left">-</td>
    516. 

  516. <td align="left">47</td>
    517. 

  517. <td align="left">[EXIMIME]</td>
    518. 

  518. </tr>
    519. 

  519. <tr class="odd">
    520. 

  520. <td align="left">application/json</td>
    521. 

  521. <td align="left">-</td>
    522. 

  522. <td align="left">50</td>
    523. 

  523. <td align="left">[RFC4627]</td>
    524. 

  524. </tr>
    525. 

  525. </tbody>
    526. 

  526. </table>
    527. 

  527. <p>简单地说就是：</p>
    528. 

  528. <p><code>诸如application/json的Content Types在CoAP中应该是50</code>。如上表所示的结果是其对应的结果，这样的话可以减少传递的信息量。</p>
    529. 

  529. <h2 id="coap-json"><span class="header-section-number">1.6</span> CoAP JSON</h2>
    530. 

  530. <p>于是在一开始的时候首先支持的便是“application/json”这样的类型。</p>
    531. 

  531. <p>首先判断请求的header</p>
    532. 

  532. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="va">request_helper</span>.<span class="at">getHandler</span> <span class="op">=</span> <span class="kw">function</span>(req<span class="op">,</span> res) <span class="op">{</span>
    533. 

  533.     <span class="cf">switch</span> (<span class="va">req</span>.<span class="at">headers</span>[<span class="st">&#39;Accept&#39;</span>]) <span class="op">{</span>
    534. 

  534.         <span class="cf">case</span> <span class="st">&quot;application/json&quot;</span><span class="op">:</span>
    535. 

  535.             <span class="va">qh</span>.<span class="at">returnJSON</span>(req<span class="op">,</span> res)<span class="op">;</span>
    536. 

  536.             <span class="cf">break</span><span class="op">;</span>
    537. 

  537.         <span class="cf">case</span> <span class="st">&quot;application/xml&quot;</span><span class="op">:</span>
    538. 

  538.             <span class="va">qh</span>.<span class="at">returnXML</span>(req<span class="op">,</span> res)<span class="op">;</span>
    539. 

  539.             <span class="cf">break</span><span class="op">;</span>
    540. 

  540.     <span class="op">}</span>
    541. 

  541. <span class="op">};</span></code></pre></div>
    542. 

  542. <p>再转至相应的函数处理，而判断的依据则是Accept是不是“application/json”。</p>
    543. 

  543. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="at">registerFormat</span>(<span class="st">&#39;text/plain&#39;</span><span class="op">,</span> <span class="dv">0</span>)
    544. 

  544. <span class="at">registerFormat</span>(<span class="st">&#39;application/link-format&#39;</span><span class="op">,</span> <span class="dv">40</span>)
    545. 

  545. <span class="at">registerFormat</span>(<span class="st">&#39;application/xml&#39;</span><span class="op">,</span> <span class="dv">41</span>)
    546. 

  546. <span class="at">registerFormat</span>(<span class="st">&#39;application/octet-stream&#39;</span><span class="op">,</span> <span class="dv">42</span>)
    547. 

  547. <span class="at">registerFormat</span>(<span class="st">&#39;application/exi&#39;</span><span class="op">,</span> <span class="dv">47</span>)
    548. 

  548. <span class="at">registerFormat</span>(<span class="st">&#39;application/json&#39;</span><span class="op">,</span> <span class="dv">50</span>)</code></pre></div>
    549. 

  549. <p>对应地我们需要在一发出请求的时候设置好Accept，要不就没有办法返回我们需要的结果。</p>
    550. 

  550. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="va">req</span>.<span class="at">setHeader</span>(<span class="st">&quot;Accept&quot;</span><span class="op">,</span> <span class="st">&quot;application/json&quot;</span>)<span class="op">;</span></code></pre></div>
    551. 

  551. <p><strong>返回JSON</strong></p>
    552. 

  552. <p>在给IoT CoAP添加了JSON支持之后，变得非常有意思，至少我们可以获得我们想要的结果。在上一篇中我们介绍了一些常用的工具——<a href="http://www.phodal.com/blog/coap-command-line-tools-set/">CoAP 命令行工具集</a>。</p>
    553. 

  553. <p><strong>CoAP客户端代码</strong></p>
    554. 

  554. <p>开始之前我们需要有一个客户端代码，以便我们的服务端可以返回正确的数据并解析</p>
    555. 

  555. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="kw">var</span> coap <span class="op">=</span> <span class="at">require</span>(<span class="st">&#39;coap&#39;</span>)<span class="op">;</span>
    556. 

  556. <span class="kw">var</span> requestURI <span class="op">=</span> <span class="st">&#39;coap://localhost/&#39;</span><span class="op">;</span>
    557. 

  557. <span class="kw">var</span> url <span class="op">=</span> <span class="at">require</span>(<span class="st">&#39;url&#39;</span>).<span class="at">parse</span>(requestURI <span class="op">+</span> <span class="st">&#39;id/1/&#39;</span>)<span class="op">;</span>
    558. 

  558. <span class="va">console</span>.<span class="at">log</span>(<span class="st">&quot;Request URL: &quot;</span> <span class="op">+</span> <span class="va">url</span>.<span class="at">href</span>)<span class="op">;</span>
    559. 

  559. <span class="kw">var</span> req <span class="op">=</span> <span class="va">coap</span>.<span class="at">request</span>(url)<span class="op">;</span>
    560. 

  560. <span class="kw">var</span> bl <span class="op">=</span> <span class="at">require</span>(<span class="st">&#39;bl&#39;</span>)<span class="op">;</span>
    561. 

  561. 

  562. <span class="va">req</span>.<span class="at">setHeader</span>(<span class="st">&quot;Accept&quot;</span><span class="op">,</span> <span class="st">&quot;application/json&quot;</span>)<span class="op">;</span>
    563. 

  563. <span class="va">req</span>.<span class="at">on</span>(<span class="st">&#39;response&#39;</span><span class="op">,</span> <span class="kw">function</span>(res) <span class="op">{</span>
    564. 

  564.   <span class="va">res</span>.<span class="at">pipe</span>(<span class="at">bl</span>(<span class="kw">function</span>(err<span class="op">,</span> data) <span class="op">{</span>
    565. 

  565.     <span class="kw">var</span> json <span class="op">=</span> <span class="va">JSON</span>.<span class="at">parse</span>(data)<span class="op">;</span>
    566. 

  566.     <span class="va">console</span>.<span class="at">log</span>(json)<span class="op">;</span>
    567. 

  567.   <span class="op">}</span>))<span class="op">;</span>
    568. 

  568. 

  569. <span class="op">}</span>)<span class="op">;</span>
    570. 

  570. 

  571. <span class="va">req</span>.<span class="at">end</span>()<span class="op">;</span></code></pre></div>
    572. 

  572. <p>代码有点长内容也有点多，但是核心是这句话：</p>
    573. 

  573. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="va">req</span>.<span class="at">setHeader</span>(<span class="st">&quot;Accept&quot;</span><span class="op">,</span> <span class="st">&quot;application/json&quot;</span>)<span class="op">;</span></code></pre></div>
    574. 

  574. <p>这样的话，我们只需要在我们的服务端一判断，</p>
    575. 

  575. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="cf">if</span>(<span class="va">req</span>.<span class="at">headers</span>[<span class="st">&#39;Accept&#39;</span>] <span class="op">==</span> <span class="st">&#39;application/json&#39;</span>) <span class="op">{</span>
    576. 

  576.      <span class="co">//do something</span>
    577. 

  577.  <span class="op">};</span></code></pre></div>
    578. 

  578. <p>这样就可以返回数据了</p>
    579. 

  579. <p><strong>CoAP Server端代码</strong></p>
    580. 

  580. <p>Server端的代码比较简单，判断一下</p>
    581. 

  581. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="cf">if</span> (<span class="va">req</span>.<span class="at">headers</span>[<span class="st">&#39;Accept&#39;</span>] <span class="op">==</span> <span class="st">&#39;application/json&#39;</span>) <span class="op">{</span>
    582. 

  582.         <span class="at">parse_url</span>(<span class="va">req</span>.<span class="at">url</span><span class="op">,</span> <span class="kw">function</span>(result)<span class="op">{</span>
    583. 

  583.             <span class="va">res</span>.<span class="at">end</span>(result)<span class="op">;</span>
    584. 

  584.         <span class="op">}</span>)<span class="op">;</span>
    585. 

  585.         <span class="va">res</span>.<span class="at">code</span> <span class="op">=</span> <span class="st">&#39;2.05&#39;</span><span class="op">;</span>
    586. 

  586.     <span class="op">}</span></code></pre></div>
    587. 

  587. <p>请求的是否是JSON格式，再返回一个205，也就是Content，只是这时设计是请求一个URL返回对应的数据。如</p>
    588. 

  588. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">coap</span>://localhost/id/1/</code></pre></div>
    589. 

  589. <p>这时应该请求的是ID为1的数据，即</p>
    590. 

  590. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript">[ <span class="op">{</span> <span class="dt">id</span><span class="op">:</span> <span class="dv">1</span><span class="op">,</span> <span class="dt">value</span><span class="op">:</span> <span class="st">&#39;is id 1&#39;</span><span class="op">,</span> <span class="dt">sensors1</span><span class="op">:</span> <span class="dv">19</span><span class="op">,</span> <span class="dt">sensors2</span><span class="op">:</span> <span class="dv">20</span> <span class="op">}</span>]</code></pre></div>
    591. 

  591. <p>而parse_url只是从数据库从读取相应的数据。</p>
    592. 

  592. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript"><span class="kw">function</span> <span class="at">parse_url</span>(url <span class="op">,</span>callback) <span class="op">{</span>
    593. 

  593.     <span class="kw">var</span> db <span class="op">=</span> <span class="kw">new</span> <span class="va">sqlite3</span>.<span class="at">Database</span>(config[<span class="st">&quot;db_name&quot;</span>])<span class="op">;</span>
    594. 

  594.     <span class="kw">var</span> result <span class="op">=</span> []<span class="op">;</span>
    595. 

  595.     <span class="va">db</span>.<span class="at">all</span>(<span class="st">&quot;SELECT * FROM basic;&quot;</span><span class="op">,</span> <span class="kw">function</span>(err<span class="op">,</span> rows) <span class="op">{</span>
    596. 

  596.         <span class="at">callback</span>(<span class="va">JSON</span>.<span class="at">stringify</span>(rows))<span class="op">;</span>
    597. 

  597.     <span class="op">}</span>)
    598. 

  598. <span class="op">}</span></code></pre></div>
    599. 

  599. <p>并且全部都显示出来，设计得真是有点不行，不过现在已经差不多了。</p>
    600. 

  600. </body>
    601. 

  601. </html>
    602.