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  46.   <link rel="stylesheet" href="css/vendor.css" type="text/css" />
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  47. </head>
    48. 

  48. <body>
    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="#http-熟悉陌生"><span class="toc-section-number">1</span> HTTP 熟悉&amp;陌生</a><ul>
    63. 

  63. <li><a href="#你所没有深入的http"><span class="toc-section-number">1.1</span> 你所没有深入的HTTP</a><ul>
    64. 

  64. <li><a href="#打开网页时发生了什么"><span class="toc-section-number">1.1.1</span> 打开网页时发生了什么</a></li>
    65. 

  65. <li><a href="#url组成"><span class="toc-section-number">1.1.2</span> URL组成</a></li>
    66. 

  66. </ul></li>
    67. 

  67. <li><a href="#一次http-get请求"><span class="toc-section-number">1.2</span> 一次HTTP GET请求</a><ul>
    68. 

  68. <li><a href="#http响应"><span class="toc-section-number">1.2.1</span> HTTP响应</a></li>
    69. 

  69. </ul></li>
    70. 

  70. </ul></li>
    71. 

  71. </ul>
    72. 

  72. </div>
    73. 

  73. <h1 id="http-熟悉陌生"><span class="header-section-number">1</span> HTTP 熟悉&amp;陌生</h1>
    74. 

  74. <h2 id="你所没有深入的http"><span class="header-section-number">1.1</span> 你所没有深入的HTTP</h2>
    75. 

  75. <p>Internet有两个核心协议: IP和TCP，这样讲述起来似乎会很漫长。</p>
    76. 

  76. <p>基本概念</p>
    77. 

  77. <blockquote>
    78. 

  78. <p>超文本传输协议 (HTTP-Hypertext transfer protocol) 是一种详细规定了浏览器和万维网服务器之间互相通信的规则，通过因特网传送万维网文档的数据传送协议。</p>
    79. 

  79. </blockquote>
    80. 

  80. <ul>
    81. 

  81. <li>HTTP是用于客户端与服务端之间的通信。</li>
    82. 

  82. <li>传输层的TCP是基于网络层的IP协议的,而应用层的HTTP协议又是基于传输层的TCP协议的。</li>
    83. 

  83. </ul>
    84. 

  84. <p><code>注意</code>: HTTP协议只规定了客户端与服务端的通信规则，而没有规定其通讯协议，只是现在的大部分实现都是将TCP作为通讯协议。</p>
    85. 

  85. <h3 id="打开网页时发生了什么"><span class="header-section-number">1.1.1</span> 打开网页时发生了什么</h3>
    86. 

  86. <p>简单地来说，当我们在浏览器上输入URL的敲下回车的时候。</p>
    87. 

  87. <ul>
    88. 

  88. <li>浏览器需要查找域名<a href="#fn1" class="footnoteRef" id="fnref1"><sup>1</sup></a>的IP，从不同的缓存直至DNS服务器。</li>
    89. 

  89. <li>浏览器会给web服务器发送一个HTTP请求</li>
    90. 

  90. <li>服务器“处理”请求</li>
    91. 

  91. <li>服务器发回一个HTML响应</li>
    92. 

  92. <li>浏览器渲染HTML到页面。</li>
    93. 

  93. </ul>
    94. 

  94. <p>在<a href="http://stackoverflow.com/questions/2092527/what-happens-when-you-type-in-a-url-in-browser">StackOverflow</a>上有一个这样的回答会比较详细。</p>
    95. 

  95. <ul>
    96. 

  96. <li>browser checks cache; if requested object is in cache and is fresh, skip to #9</li>
    97. 

  97. <li>browser asks OS for server’s IP address</li>
    98. 

  98. <li>OS makes a DNS lookup and replies the IP address to the browser</li>
    99. 

  99. <li>browser opens a TCP connection to server (this step is much more complex with HTTPS)</li>
    100. 

  100. <li>browser sends the HTTP request through TCP connection</li>
    101. 

  101. <li>browser receives HTTP response and may close the TCP connection, or reuse it for another request</li>
    102. 

  102. <li>browser checks if the response is a redirect (3xx result status codes), authorization request (401), error (4xx and 5xx), etc.; these are handled differently from normal responses (2xx)</li>
    103. 

  103. <li>if cacheable, response is stored in cache</li>
    104. 

  104. <li>browser decodes response (e.g. if it’s gzipped)</li>
    105. 

  105. <li>browser determines what to do with response (e.g. is it a HTML page, is it an image, is it a sound clip?)</li>
    106. 

  106. <li>browser renders response, or offers a download dialog for unrecognized types</li>
    107. 

  107. </ul>
    108. 

  108. <p>忽略一些细节便剩下了</p>
    109. 

  109. <ol style="list-style-type: decimal">
    110. 

  110. <li>从浏览器输入URL</li>
    111. 

  111. <li>浏览器找到服务器，服务器返回HTML文档</li>
    112. 

  112. <li>从对应的服务器下载资源</li>
    113. 

  113. </ol>
    114. 

  114. <p>说说第一步，开始时我们输入的是URI(统一资源标识符,Uniform Resource Identifier)，它还有另外一个名字叫统一资源定位器(URL<a href="#fn2" class="footnoteRef" id="fnref2"><sup>2</sup></a>,Uniform Resource Locator)。</p>
    115. 

  115. <h3 id="url组成"><span class="header-section-number">1.1.2</span> URL组成</h3>
    116. 

  116. <p>网址算是URL的一个俗称，让我们来看看一个URL的组成，以HTTP版IOT中的URL为例。</p>
    117. 

  117. <p><code>http://b.phodal.com/athome/1</code></p>
    118. 

  118. <p>开始之前，我们需要标出URL的80端口以及json文件的全称，那么上面的网址就会变成</p>
    119. 

  119. <p><code>http://b.phodal.com:80/athome/1.json</code></p>
    120. 

  120. <p>那么对于这个URL的就有下面几部分组成</p>
    121. 

  121. <ul>
    122. 

  122. <li><code>http://</code> http说的是这个URL用的是HTTP协议，至于<code>//</code>是一个分隔符，用法和C语言中的<code>;</code>一样。这样的协议还可以是coap,https,ftp等等。</li>
    123. 

  123. <li><code>b</code> 是子域名，一个域名在<strong>允许</strong>的情况下可以有不限数量的子域名。</li>
    124. 

  124. <li><code>phodal.com</code> 代表了一个URL是phodal.com下面的域名</li>
    125. 

  125. <li><code>80</code> 80是指80端口，默认的都是80，对于一个不是80端口的URL应该是这样的<code>http://iot-coap.phodal.com:8896/</code></li>
    126. 

  126. <li><code>athome</code> 指的是虚拟目录部分，或者文件路径</li>
    127. 

  127. <li><code>1.json</code>看上去就是一个文件名，然而也代表着这是一个资源。</li>
    128. 

  128. </ul>
    129. 

  129. <p>对就一个稍微复杂点的例子就是</p>
    130. 

  130. <p><code>http://ebook.designiot.cn/#你所没有深入的http</code></p>
    131. 

  131. <p>这里的<code>#</code>后面是锚部分，如果你打开这个URL就会发现会直接跳转到相应的锚部分，对就于下面这样的一个例子来说</p>
    132. 

  132. <p><code>http://www.phodal.com/search/?q=iot&amp;type=blog</code></p>
    133. 

  133. <p><code>?</code>后面的<code>q=iot&amp;type=blog</code>的部分是参数部分，通常用于查询或者、搜索。</p>
    134. 

  134. <h2 id="一次http-get请求"><span class="header-section-number">1.2</span> 一次HTTP GET请求</h2>
    135. 

  135. <p>当我们打开最小物联网系统的一个页面时，如<a href="http://b.phodal.com/athome/1.json" class="uri">http://b.phodal.com/athome/1.json</a></p>
    136. 

  136. <p>我们在浏览器上看到的结果是</p>
    137. 

  137. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript">[
    138. 

  138.   <span class="op">{</span>
    139. 

  139.     <span class="st">&quot;id&quot;</span><span class="op">:</span> <span class="dv">1</span><span class="op">,</span>
    140. 

  140.     <span class="st">&quot;temperature&quot;</span><span class="op">:</span> <span class="dv">19</span><span class="op">,</span>
    141. 

  141.     <span class="st">&quot;sensors1&quot;</span><span class="op">:</span> <span class="dv">31</span><span class="op">,</span>
    142. 

  142.     <span class="st">&quot;sensors2&quot;</span><span class="op">:</span> <span class="fl">7.5</span><span class="op">,</span>
    143. 

  143.     <span class="st">&quot;led1&quot;</span><span class="op">:</span> <span class="dv">0</span>
    144. 

  144.   <span class="op">}</span>
    145. 

  145. ]</code></pre></div>
    146. 

  146. <p>只是我们看到的是结果，忽略了这其中的过程，于是我们用curl<a href="#fn3" class="footnoteRef" id="fnref3"><sup>3</sup></a>命令来看看详细的情况。</p>
    147. 

  147. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">curl</span> -I -s http://b.phodal.com/athome/1.json</code></pre></div>
    148. 

  148. <p>出于某种原因考虑，删去了其中一些元素，剩下下面这些。</p>
    149. 

  149. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">HTTP/1.1</span> 200 OK
    150. 

  150. <span class="kw">Content-Type</span>: application/json
    151. 

  151. <span class="kw">Date</span>: Fri, 05 Sep 2014 15:05:49 GMT
    152. 

  152. 

  153. [<span class="dt">{&quot;id&quot;:1,&quot;temperature&quot;:19,&quot;sensors1&quot;:31,&quot;sensors2&quot;:7.5,&quot;led1&quot;:0}</span>]</code></pre></div>
    154. 

  154. <p>我们用curl命令向服务器发起了GET请求，服务器返回了上面的结果。</p>
    155. 

  155. <h3 id="http响应"><span class="header-section-number">1.2.1</span> HTTP响应</h3>
    156. 

  156. <p>一个HTTP响应由三部分组成</p>
    157. 

  157. <ul>
    158. 

  158. <li>状态行(状态码)</li>
    159. 

  159. <li>消息报头(响应报头)</li>
    160. 

  160. <li>响应正文(消息体)</li>
    161. 

  161. </ul>
    162. 

  162. <h4 id="http响应-状态码"><span class="header-section-number">1.2.1.1</span> HTTP响应 状态码</h4>
    163. 

  163. <p>在上面的结果中，状态行是</p>
    164. 

  164. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">HTTP/1.1</span> 200 OK</code></pre></div>
    165. 

  165. <p>返回的状态码是200，OK是状态码的原因短语。</p>
    166. 

  166. <p>如果是一个跳转的页面，它就可能是下面的结果:</p>
    167. 

  167. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">HTTP/1.0</span> 301 MOVED PERMANENTLY
    168. 

  168. <span class="kw">Date</span>: Mon, 08 Sep 2014 12:04:01 GMT
    169. 

  169. <span class="kw">Content-Type</span>: text/html<span class="kw">;</span> <span class="ot">charset=</span>utf-8  </code></pre></div>
    170. 

  170. <p>HTTP Status有五种状态，而这五种状态又有所细分，提一下这五种状态，详细可参见<a href="http://zh.wikipedia.org/wiki/HTTP%E7%8A%B6%E6%80%81%E7%A0%81">http://zh.wikipedia.org/wiki/HTTP%E7%8A%B6%E6%80%81%E7%A0%81</a></p>
    171. 

  171. <ul>
    172. 

  172. <li>1xx消息</li>
    173. 

  173. <li>2xx成功</li>
    174. 

  174. <li>3xx重定向</li>
    175. 

  175. <li>4xx客户端错误</li>
    176. 

  176. <li>5xx服务器错误</li>
    177. 

  177. </ul>
    178. 

  178. <p>如</p>
    179. 

  179. <ul>
    180. 

  180. <li>200 ok - 成功返回状态，对应，GET,PUT,PATCH,DELETE.</li>
    181. 

  181. <li>201 created - 成功创建。</li>
    182. 

  182. <li>304 not modified - HTTP缓存有效。</li>
    183. 

  183. <li>400 bad request - 请求格式错误。</li>
    184. 

  184. <li>401 unauthorized - 未授权。</li>
    185. 

  185. <li>403 forbidden - 鉴权成功，但是该用户没有权限。</li>
    186. 

  186. <li>404 not found - 请求的资源不存在</li>
    187. 

  187. <li>405 method not allowed - 该http方法不被允许。</li>
    188. 

  188. <li>410 gone - 这个url对应的资源现在不可用。</li>
    189. 

  189. <li>415 unsupported media type - 请求类型错误。</li>
    190. 

  190. <li>422 unprocessable entity - 校验错误时用。</li>
    191. 

  191. <li>429 too many request - 请求过多。</li>
    192. 

  192. </ul>
    193. 

  193. <h4 id="http响应-响应报头"><span class="header-section-number">1.2.1.2</span> HTTP响应 响应报头</h4>
    194. 

  194. <p>在这次响应中，返回了两个报头，即</p>
    195. 

  195. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">Content-Type</span>: application/json
    196. 

  196. <span class="kw">Date</span>: Fri, 05 Sep 2014 15:05:49 GMT</code></pre></div>
    197. 

  197. <p>Content-Type和Date，在这里的Context-Type是application/json，而通常情况下我们打开一个网站时，他的Content-Type应该是text/html。</p>
    198. 

  198. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">Content-Type</span>: text/html<span class="kw">;</span></code></pre></div>
    199. 

  199. <p>Content-Type是最重要的报头。</p>
    200. 

  200. <h4 id="http响应-响应正文"><span class="header-section-number">1.2.1.3</span> HTTP响应 响应正文</h4>
    201. 

  201. <p>正文才是我们真正想要的内容，上面的都是写给浏览器看的，一般的人不会去关注这些。</p>
    202. 

  202. <div class="sourceCode"><pre class="sourceCode javascript"><code class="sourceCode javascript">HTTP/<span class="fl">1.1</span> <span class="dv">200</span> OK
    203. 

  203. Server<span class="op">:</span> <span class="va">phodal</span>.<span class="at">com</span>/<span class="fl">0.17.5</span>
    204. 

  204. Content<span class="op">-</span>Type<span class="op">:</span> application/json
    205. 

  205. 

  206. [<span class="op">{</span><span class="st">&quot;id&quot;</span><span class="op">:</span><span class="dv">1</span><span class="op">,</span><span class="st">&quot;temperature&quot;</span><span class="op">:</span><span class="dv">19</span><span class="op">,</span><span class="st">&quot;sensors1&quot;</span><span class="op">:</span><span class="dv">31</span><span class="op">,</span><span class="st">&quot;sensors2&quot;</span><span class="op">:</span><span class="fl">7.5</span><span class="op">,</span><span class="st">&quot;led1&quot;</span><span class="op">:</span><span class="dv">0</span><span class="op">}</span>]</code></pre></div>
    207. 

  207. <p>通常这是以某种格式写的，在这里是以JSON写的，而对于一个网站的时候则是HTML，如:</p>
    208. 

  208. <div class="sourceCode"><pre class="sourceCode html"><code class="sourceCode html"><span class="kw">&lt;html&gt;</span>
    209. 

  209. <span class="kw">&lt;head&gt;</span>
    210. 

  210.     <span class="kw">&lt;meta</span><span class="ot"> charset=</span><span class="st">&quot;UTF-8&quot;</span><span class="kw">&gt;</span>
    211. 

  211.     <span class="kw">&lt;title&gt;</span>Document<span class="kw">&lt;/title&gt;</span>
    212. 

  212. <span class="kw">&lt;/head&gt;</span>
    213. 

  213. <span class="kw">&lt;body&gt;</span>
    214. 

  214.     
    215. 

  215. <span class="kw">&lt;/body&gt;</span>
    216. 

  216. <span class="kw">&lt;/html&gt;</span>     </code></pre></div>
    217. 

  217. <p>那么这次GET请求返回的就是:</p>
    218. 

  218. <div class="sourceCode"><pre class="sourceCode bash"><code class="sourceCode bash"><span class="kw">HTTP/1.0</span> 200 OK
    219. 

  219. <span class="kw">Date</span>: Mon, 08 Sep 2014 12:04:01 GMT
    220. 

  220. <span class="kw">Content-Type</span>: text/html<span class="kw">;</span> <span class="ot">charset=</span>utf-8  
    221. 

  221. 

  222. <span class="kw">&lt;html&gt;</span>
    223. 

  223. <span class="kw">&lt;head&gt;</span>
    224. 

  224.     <span class="kw">&lt;meta</span> charset=<span class="st">&quot;UTF-8&quot;</span><span class="kw">&gt;</span>
    225. 

  225.     <span class="kw">&lt;title&gt;</span>Document<span class="kw">&lt;</span>/title<span class="kw">&gt;</span>
    226. 

  226. <span class="kw">&lt;</span>/<span class="kw">head&gt;</span>
    227. 

  227. <span class="kw">&lt;body&gt;</span>
    228. 

  228.     [<span class="dt">{&quot;id&quot;:1,&quot;temperature&quot;:19,&quot;sensors1&quot;:31,&quot;sensors2&quot;:7.5,&quot;led1&quot;:0}</span>]       
    229. 

  229. <span class="kw">&lt;</span>/<span class="kw">body&gt;</span>
    230. 

  230. <span class="kw">&lt;</span>/<span class="kw">html&gt;</span> </code></pre></div>
    231. 

  231. <p>虽然与第一次请求的结果在游览器上看似乎是一样的(ps:可能有微小的差异)，然而其本质是不同的。</p>
    232. 

  232. <p>推荐及参考书目：</p>
    233. 

  233. <ul>
    234. 

  234. <li>《Web性能权威指南》</li>
    235. 

  235. <li>《图解HTTP》</li>
    236. 

  236. <li>《RESTful Web Services Cookbook》</li>
    237. 

  237. <li>《RESTful Web APIs》</li>
    238. 

  238. </ul>
    239. 

  239. <div class="footnotes">
    240. 

  240. <hr />
    241. 

  241. <ol>
    242. 

  242. <li id="fn1"><p>形如http://www.phodal.com<a href="#fnref1">↩</a></p></li>
    243. 

  243. <li id="fn2"><p>URL 是 URI 的子集<a href="#fnref2">↩</a></p></li>
    244. 

  244. <li id="fn3"><p>curl是利用URL语法在命令行方式下工作的开源文件传输工具。<a href="#fnref3">↩</a></p></li>
    245. 

  245. </ol>
    246. 

  246. </div>
    247. 

  247. </body>
    248. 

  248. </html>
    249.