Inicio Explorar Axuda
Iniciar sesión
ded
/
cpp-httplib
réplica de https://github.com/yhirose/cpp-httplib.git
1
0
Fork 0
Ficheiros Incidencias 0 Wiki
Árbore: cda9680cdc
Ramas Etiquetas
cpp-httplib
/
docs
/
en
/
tour
/
03-basic-server
/
index.html

index.html 60 KB
Histórico Raw

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400401402403404405406407408409410411412413414415416417418419420421422423424425426427428429430431432433434435436437438439440441442443444445446447448449450451452453454455456457458459460461462463464465466467 
  1. <!DOCTYPE html>
    2. 

  2. <html lang="en" data-base-path="&#x2F;cpp-httplib">
    3. 

  3. <head>
    4. 

  4.   <meta charset="utf-8">
    5. 

  5.   <meta name="viewport" content="width=device-width, initial-scale=1">
    6. 

  6.   <title>Basic Server - cpp-httplib</title>
    7. 

  7.   <link rel="icon" type="image/svg+xml" href="&#x2F;cpp-httplib/favicon.svg">
    8. 

  8.   <link rel="stylesheet" href="&#x2F;cpp-httplib/css/main.css">
    9. 

  9.   <script>
    10. 

  10.     (function() {
    11. 

  11.       var t = localStorage.getItem('preferred-theme');
    12. 

  12.       if (!t) t = window.matchMedia('(prefers-color-scheme: light)').matches ? 'light' : 'dark';
    13. 

  13.       if (t === 'light') document.documentElement.setAttribute('data-theme', 'light');
    14. 

  14.     })();
    15. 

  15.   </script>
    16. 

  16. </head>
    17. 

  17. <body>
    18. 

  18.   <header class="header">
    19. 

  19.     <div class="header-inner">
    20. 

  20.       <a href="&#x2F;cpp-httplib/en/" class="header-title">cpp-httplib <span style="font-size:0.75em;font-weight:normal;margin-left:4px">v0.35.0</span></a>
    21. 

  21.       <div class="header-spacer"></div>
    22. 

  22.       <nav class="header-nav">
    23. 

  23.         <a href="&#x2F;cpp-httplib/en/">
    24. 

  24.           <svg xmlns="http://www.w3.org/2000/svg" width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M3 9l9-7 9 7v11a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2z"/><polyline points="9 22 9 12 15 12 15 22"/></svg>
    25. 

  25.           Home
    26. 

  26.         </a>
    27. 

  27.         
    28. 

  28.         
    29. 

  29.         <a href="&#x2F;cpp-httplib/en/tour&#x2F;">
    30. 

  30.           <svg xmlns="http://www.w3.org/2000/svg" width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="12" r="10"/><polygon points="16.24 7.76 14.12 14.12 7.76 16.24 9.88 9.88 16.24 7.76"/></svg>
    31. 

  31.           Tour
    32. 

  32.         </a>
    33. 

  33.         
    34. 

  34.         
    35. 

  35.         
    36. 

  36.         <a href="https:&#x2F;&#x2F;github.com&#x2F;yhirose&#x2F;cpp-httplib" aria-label="GitHub">
    37. 

  37.           <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M9 19c-5 1.5-5-2.5-7-3m14 6v-3.87a3.37 3.37 0 0 0-.94-2.61c3.14-.35 6.44-1.54 6.44-7A5.44 5.44 0 0 0 20 4.77 5.07 5.07 0 0 0 19.91 1S18.73.65 16 2.48a13.38 13.38 0 0 0-7 0C6.27.65 5.09 1 5.09 1A5.07 5.07 0 0 0 5 4.77a5.44 5.44 0 0 0-1.5 3.78c0 5.42 3.3 6.61 6.44 7A3.37 3.37 0 0 0 9 18.13V22"/></svg>
    38. 

  38.           GitHub
    39. 

  39.         </a>
    40. 

  40.         
    41. 

  41.         
    42. 

  42.       </nav>
    43. 

  43.       <div class="header-tools">
    44. 

  44.         <button class="theme-toggle" aria-label="Toggle theme"></button>
    45. 

  45.         <div class="lang-selector">
    46. 

  46.           <button class="lang-btn" aria-label="Language">
    47. 

  47.             <svg xmlns="http://www.w3.org/2000/svg" width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="12" r="10"/><line x1="2" y1="12" x2="22" y2="12"/><path d="M12 2a15.3 15.3 0 0 1 4 10 15.3 15.3 0 0 1-4 10 15.3 15.3 0 0 1-4-10 15.3 15.3 0 0 1 4-10z"/></svg>
    48. 

  48.             EN
    49. 

  49.           </button>
    50. 

  50.           <ul class="lang-popup">
    51. 

  51.             
    52. 

  52.             <li><a href="#" data-lang="en">EN</a></li>
    53. 

  53.             
    54. 

  54.             <li><a href="#" data-lang="ja">JA</a></li>
    55. 

  55.             
    56. 

  56.           </ul>
    57. 

  57.         </div>
    58. 

  58.       </div>
    59. 

  59.       <button class="sidebar-toggle" aria-label="Menu">&#9776;</button>
    60. 

  60.     </div>
    61. 

  61.   </header>
    62. 

  62. 

  63.   
    64. 

  64. 

  65.   <div class="layout has-sidebar">
    66. 

  66.     
    67. 

  67. <aside class="sidebar">
    68. 

  68.   <nav class="sidebar-nav">
    69. 

  69.     
    70. 

  70.     <div class="nav-section">
    71. 

  71.       <a href="&#x2F;cpp-httplib&#x2F;en&#x2F;tour&#x2F;" class="nav-section-title active">A Tour of cpp-httplib</a>
    72. 

  72.       
    73. 

  73.       <ul class="nav-list">
    74. 

  74.         
    75. 

  75.         <li><a href="&#x2F;cpp-httplib&#x2F;en&#x2F;tour&#x2F;01-getting-started&#x2F;" class="">Getting Started</a></li>
    76. 

  76.         
    77. 

  77.         <li><a href="&#x2F;cpp-httplib&#x2F;en&#x2F;tour&#x2F;02-basic-client&#x2F;" class="">Basic Client</a></li>
    78. 

  78.         
    79. 

  79.         <li><a href="&#x2F;cpp-httplib&#x2F;en&#x2F;tour&#x2F;03-basic-server&#x2F;" class="active">Basic Server</a></li>
    80. 

  80.         
    81. 

  81.         <li><a href="&#x2F;cpp-httplib&#x2F;en&#x2F;tour&#x2F;04-static-file-server&#x2F;" class="">Static File Server</a></li>
    82. 

  82.         
    83. 

  83.         <li><a href="&#x2F;cpp-httplib&#x2F;en&#x2F;tour&#x2F;05-tls-setup&#x2F;" class="">TLS Setup</a></li>
    84. 

  84.         
    85. 

  85.         <li><a href="&#x2F;cpp-httplib&#x2F;en&#x2F;tour&#x2F;06-https-client&#x2F;" class="">HTTPS Client</a></li>
    86. 

  86.         
    87. 

  87.         <li><a href="&#x2F;cpp-httplib&#x2F;en&#x2F;tour&#x2F;07-https-server&#x2F;" class="">HTTPS Server</a></li>
    88. 

  88.         
    89. 

  89.         <li><a href="&#x2F;cpp-httplib&#x2F;en&#x2F;tour&#x2F;08-websocket&#x2F;" class="">WebSocket</a></li>
    90. 

  90.         
    91. 

  91.         <li><a href="&#x2F;cpp-httplib&#x2F;en&#x2F;tour&#x2F;09-whats-next&#x2F;" class="">What&#x27;s Next</a></li>
    92. 

  92.         
    93. 

  93.       </ul>
    94. 

  94.       
    95. 

  95.     </div>
    96. 

  96.     
    97. 

  97.   </nav>
    98. 

  98. </aside>
    99. 

  99. <main class="content">
    100. 

  100.   <article>
    101. 

  101.     <h1>Basic Server</h1>
    102. 

  102.     <p>In the previous chapter, you sent requests from a client to a test server. Now let's walk through how that server actually works.</p>
    103. 

  103. <h2>Starting the Server</h2>
    104. 

  104. <p>Once you've registered your routes, call <code>svr.listen()</code> to start the server.</p>
    105. 

  105. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    106. 

  106. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">listen</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">0.0.0.0</span><span style="color:#d3d0c8;">&quot;, </span><span style="color:#f99157;">8080</span><span style="color:#d3d0c8;">);
    107. 

  107. </span></pre>
    108. 

  108. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    109. 

  109. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">listen</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">0.0.0.0</span><span style="color:#4f5b66;">&quot;, </span><span style="color:#d08770;">8080</span><span style="color:#4f5b66;">);
    110. 

  110. </span></pre>
    111. 

  111. </div>
    112. 

  112. <p>The first argument is the host, and the second is the port. <code>"0.0.0.0"</code> listens on all network interfaces. Use <code>"127.0.0.1"</code> if you want to accept connections from your own machine only.</p>
    113. 

  113. <p><code>listen()</code> is a blocking call. It won't return until the server stops. The server keeps running until you press <code>Ctrl+C</code> in your terminal or call <code>svr.stop()</code> from another thread.</p>
    114. 

  114. <h2>Routing</h2>
    115. 

  115. <p>Routing is the heart of any server. It's how you tell cpp-httplib: when a request comes in for this URL with this HTTP method, run this code.</p>
    116. 

  116. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    117. 

  117. <span style="color:#d3d0c8;">httplib::Server svr;
    118. 

  118. </span><span style="color:#d3d0c8;">
    119. 

  119. </span><span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/hi</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const</span><span style="color:#d3d0c8;"> httplib::Request &amp;req, httplib::Response &amp;res) {
    120. 

  120. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">Hello!</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    121. 

  121. </span><span style="color:#d3d0c8;">});
    122. 

  122. </span></pre>
    123. 

  123. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    124. 

  124. <span style="color:#4f5b66;">httplib::Server svr;
    125. 

  125. </span><span style="color:#4f5b66;">
    126. 

  126. </span><span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/hi</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const</span><span style="color:#4f5b66;"> httplib::Request &amp;req, httplib::Response &amp;res) {
    127. 

  127. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">Hello!</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    128. 

  128. </span><span style="color:#4f5b66;">});
    129. 

  129. </span></pre>
    130. 

  130. </div>
    131. 

  131. <p><code>svr.Get()</code> registers a handler for GET requests. The first argument is the path, the second is the handler function. When a GET request arrives at <code>/hi</code>, your lambda runs.</p>
    132. 

  132. <p>There's a method for each HTTP verb.</p>
    133. 

  133. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    134. 

  134. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/path</span><span style="color:#d3d0c8;">&quot;,    handler);  </span><span style="color:#747369;">// GET
    135. 

  135. </span><span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Post</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/path</span><span style="color:#d3d0c8;">&quot;,   handler);  </span><span style="color:#747369;">// POST
    136. 

  136. </span><span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Put</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/path</span><span style="color:#d3d0c8;">&quot;,    handler);  </span><span style="color:#747369;">// PUT
    137. 

  137. </span><span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Delete</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/path</span><span style="color:#d3d0c8;">&quot;, handler);  </span><span style="color:#747369;">// DELETE
    138. 

  138. </span></pre>
    139. 

  139. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    140. 

  140. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/path</span><span style="color:#4f5b66;">&quot;,    handler);  </span><span style="color:#a7adba;">// GET
    141. 

  141. </span><span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Post</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/path</span><span style="color:#4f5b66;">&quot;,   handler);  </span><span style="color:#a7adba;">// POST
    142. 

  142. </span><span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Put</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/path</span><span style="color:#4f5b66;">&quot;,    handler);  </span><span style="color:#a7adba;">// PUT
    143. 

  143. </span><span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Delete</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/path</span><span style="color:#4f5b66;">&quot;, handler);  </span><span style="color:#a7adba;">// DELETE
    144. 

  144. </span></pre>
    145. 

  145. </div>
    146. 

  146. <p>The handler signature is <code>(const httplib::Request &amp;req, httplib::Response &amp;res)</code>. You can use <code>auto</code> to keep it short.</p>
    147. 

  147. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    148. 

  148. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/hi</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    149. 

  149. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">Hello!</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    150. 

  150. </span><span style="color:#d3d0c8;">});
    151. 

  151. </span></pre>
    152. 

  152. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    153. 

  153. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/hi</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    154. 

  154. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">Hello!</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    155. 

  155. </span><span style="color:#4f5b66;">});
    156. 

  156. </span></pre>
    157. 

  157. </div>
    158. 

  158. <p>The handler only runs when the path matches. Requests to unregistered paths automatically return 404.</p>
    159. 

  159. <h2>The Request Object</h2>
    160. 

  160. <p>The first parameter <code>req</code> gives you everything the client sent.</p>
    161. 

  161. <h3>Body</h3>
    162. 

  162. <p><code>req.body</code> holds the request body as a <code>std::string</code>.</p>
    163. 

  163. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    164. 

  164. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Post</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/post</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    165. 

  165. </span><span style="color:#d3d0c8;">    </span><span style="color:#747369;">// Echo the body back to the client
    166. 

  166. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(req.</span><span style="color:#f2777a;">body</span><span style="color:#d3d0c8;">, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    167. 

  167. </span><span style="color:#d3d0c8;">});
    168. 

  168. </span></pre>
    169. 

  169. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    170. 

  170. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Post</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/post</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    171. 

  171. </span><span style="color:#4f5b66;">    </span><span style="color:#a7adba;">// Echo the body back to the client
    172. 

  172. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(req.</span><span style="color:#bf616a;">body</span><span style="color:#4f5b66;">, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    173. 

  173. </span><span style="color:#4f5b66;">});
    174. 

  174. </span></pre>
    175. 

  175. </div>
    176. 

  176. <h3>Headers</h3>
    177. 

  177. <p>Use <code>req.get_header_value()</code> to read a request header.</p>
    178. 

  178. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    179. 

  179. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/check</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    180. 

  180. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> auth = req.</span><span style="color:#6699cc;">get_header_value</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">Authorization</span><span style="color:#d3d0c8;">&quot;);
    181. 

  181. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">Auth: </span><span style="color:#d3d0c8;">&quot; + auth, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    182. 

  182. </span><span style="color:#d3d0c8;">});
    183. 

  183. </span></pre>
    184. 

  184. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    185. 

  185. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/check</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    186. 

  186. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> auth = req.</span><span style="color:#8fa1b3;">get_header_value</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">Authorization</span><span style="color:#4f5b66;">&quot;);
    187. 

  187. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">Auth: </span><span style="color:#4f5b66;">&quot; + auth, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    188. 

  188. </span><span style="color:#4f5b66;">});
    189. 

  189. </span></pre>
    190. 

  190. </div>
    191. 

  191. <h3>Query Parameters and Form Data</h3>
    192. 

  192. <p><code>req.get_param_value()</code> retrieves a parameter by name. It works for both GET query parameters and POST form data.</p>
    193. 

  193. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    194. 

  194. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/search</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    195. 

  195. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> q = req.</span><span style="color:#6699cc;">get_param_value</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">q</span><span style="color:#d3d0c8;">&quot;);
    196. 

  196. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">Query: </span><span style="color:#d3d0c8;">&quot; + q, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    197. 

  197. </span><span style="color:#d3d0c8;">});
    198. 

  198. </span></pre>
    199. 

  199. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    200. 

  200. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/search</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    201. 

  201. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> q = req.</span><span style="color:#8fa1b3;">get_param_value</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">q</span><span style="color:#4f5b66;">&quot;);
    202. 

  202. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">Query: </span><span style="color:#4f5b66;">&quot; + q, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    203. 

  203. </span><span style="color:#4f5b66;">});
    204. 

  204. </span></pre>
    205. 

  205. </div>
    206. 

  206. <p>A request to <code>/search?q=cpp-httplib</code> gives you <code>"cpp-httplib"</code> for <code>q</code>.</p>
    207. 

  207. <p>To loop over all parameters, use <code>req.params</code>.</p>
    208. 

  208. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    209. 

  209. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Post</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/submit</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    210. 

  210. </span><span style="color:#d3d0c8;">    std::string result;
    211. 

  211. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">for </span><span style="color:#d3d0c8;">(</span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;[key, val] : req.</span><span style="color:#f2777a;">params</span><span style="color:#d3d0c8;">) {
    212. 

  212. </span><span style="color:#d3d0c8;">        result += key + &quot;</span><span style="color:#99cc99;"> = </span><span style="color:#d3d0c8;">&quot; + val + &quot;</span><span style="color:#66cccc;">\n</span><span style="color:#d3d0c8;">&quot;;
    213. 

  213. </span><span style="color:#d3d0c8;">    }
    214. 

  214. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(result, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    215. 

  215. </span><span style="color:#d3d0c8;">});
    216. 

  216. </span></pre>
    217. 

  217. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    218. 

  218. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Post</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/submit</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    219. 

  219. </span><span style="color:#4f5b66;">    std::string result;
    220. 

  220. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">for </span><span style="color:#4f5b66;">(</span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;[key, val] : req.</span><span style="color:#bf616a;">params</span><span style="color:#4f5b66;">) {
    221. 

  221. </span><span style="color:#4f5b66;">        result += key + &quot;</span><span style="color:#a3be8c;"> = </span><span style="color:#4f5b66;">&quot; + val + &quot;</span><span style="color:#96b5b4;">\n</span><span style="color:#4f5b66;">&quot;;
    222. 

  222. </span><span style="color:#4f5b66;">    }
    223. 

  223. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(result, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    224. 

  224. </span><span style="color:#4f5b66;">});
    225. 

  225. </span></pre>
    226. 

  226. </div>
    227. 

  227. <h3>File Uploads</h3>
    228. 

  228. <p>Files uploaded via multipart form data are available through <code>req.form.get_file()</code>.</p>
    229. 

  229. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    230. 

  230. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Post</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/upload</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    231. 

  231. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> f = req.</span><span style="color:#f2777a;">form</span><span style="color:#d3d0c8;">.</span><span style="color:#6699cc;">get_file</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">file</span><span style="color:#d3d0c8;">&quot;);
    232. 

  232. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> content = f.</span><span style="color:#f2777a;">filename </span><span style="color:#d3d0c8;">+ &quot;</span><span style="color:#99cc99;"> (</span><span style="color:#d3d0c8;">&quot; + </span><span style="color:#6699cc;">std::to_string</span><span style="color:#d3d0c8;">(f.</span><span style="color:#f2777a;">content</span><span style="color:#d3d0c8;">.</span><span style="color:#6699cc;">size</span><span style="color:#d3d0c8;">()) + &quot;</span><span style="color:#99cc99;"> bytes)</span><span style="color:#d3d0c8;">&quot;;
    233. 

  233. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(content, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    234. 

  234. </span><span style="color:#d3d0c8;">});
    235. 

  235. </span></pre>
    236. 

  236. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    237. 

  237. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Post</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/upload</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    238. 

  238. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> f = req.</span><span style="color:#bf616a;">form</span><span style="color:#4f5b66;">.</span><span style="color:#8fa1b3;">get_file</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">file</span><span style="color:#4f5b66;">&quot;);
    239. 

  239. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> content = f.</span><span style="color:#bf616a;">filename </span><span style="color:#4f5b66;">+ &quot;</span><span style="color:#a3be8c;"> (</span><span style="color:#4f5b66;">&quot; + </span><span style="color:#8fa1b3;">std::to_string</span><span style="color:#4f5b66;">(f.</span><span style="color:#bf616a;">content</span><span style="color:#4f5b66;">.</span><span style="color:#8fa1b3;">size</span><span style="color:#4f5b66;">()) + &quot;</span><span style="color:#a3be8c;"> bytes)</span><span style="color:#4f5b66;">&quot;;
    240. 

  240. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(content, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    241. 

  241. </span><span style="color:#4f5b66;">});
    242. 

  242. </span></pre>
    243. 

  243. </div>
    244. 

  244. <p><code>f.filename</code> gives you the filename, and <code>f.content</code> gives you the file data.</p>
    245. 

  245. <h2>Path Parameters</h2>
    246. 

  246. <p>Sometimes you want to capture part of the URL as a variable -- for example, the <code>42</code> in <code>/users/42</code>. Use the <code>:param</code> syntax to do that.</p>
    247. 

  247. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    248. 

  248. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/users/:id</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    249. 

  249. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> id = req.</span><span style="color:#f2777a;">path_params</span><span style="color:#d3d0c8;">.</span><span style="color:#6699cc;">at</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">id</span><span style="color:#d3d0c8;">&quot;);
    250. 

  250. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">User ID: </span><span style="color:#d3d0c8;">&quot; + id, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    251. 

  251. </span><span style="color:#d3d0c8;">});
    252. 

  252. </span></pre>
    253. 

  253. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    254. 

  254. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/users/:id</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    255. 

  255. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> id = req.</span><span style="color:#bf616a;">path_params</span><span style="color:#4f5b66;">.</span><span style="color:#8fa1b3;">at</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">id</span><span style="color:#4f5b66;">&quot;);
    256. 

  256. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">User ID: </span><span style="color:#4f5b66;">&quot; + id, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    257. 

  257. </span><span style="color:#4f5b66;">});
    258. 

  258. </span></pre>
    259. 

  259. </div>
    260. 

  260. <p>A request to <code>/users/42</code> gives you <code>"42"</code> from <code>req.path_params.at("id")</code>. <code>/users/100</code> gives you <code>"100"</code>.</p>
    261. 

  261. <p>You can capture multiple segments at once.</p>
    262. 

  262. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    263. 

  263. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/users/:user_id/posts/:post_id</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    264. 

  264. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> user_id = req.</span><span style="color:#f2777a;">path_params</span><span style="color:#d3d0c8;">.</span><span style="color:#6699cc;">at</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">user_id</span><span style="color:#d3d0c8;">&quot;);
    265. 

  265. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> post_id = req.</span><span style="color:#f2777a;">path_params</span><span style="color:#d3d0c8;">.</span><span style="color:#6699cc;">at</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">post_id</span><span style="color:#d3d0c8;">&quot;);
    266. 

  266. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">User: </span><span style="color:#d3d0c8;">&quot; + user_id + &quot;</span><span style="color:#99cc99;">, Post: </span><span style="color:#d3d0c8;">&quot; + post_id, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    267. 

  267. </span><span style="color:#d3d0c8;">});
    268. 

  268. </span></pre>
    269. 

  269. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    270. 

  270. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/users/:user_id/posts/:post_id</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    271. 

  271. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> user_id = req.</span><span style="color:#bf616a;">path_params</span><span style="color:#4f5b66;">.</span><span style="color:#8fa1b3;">at</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">user_id</span><span style="color:#4f5b66;">&quot;);
    272. 

  272. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> post_id = req.</span><span style="color:#bf616a;">path_params</span><span style="color:#4f5b66;">.</span><span style="color:#8fa1b3;">at</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">post_id</span><span style="color:#4f5b66;">&quot;);
    273. 

  273. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">User: </span><span style="color:#4f5b66;">&quot; + user_id + &quot;</span><span style="color:#a3be8c;">, Post: </span><span style="color:#4f5b66;">&quot; + post_id, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    274. 

  274. </span><span style="color:#4f5b66;">});
    275. 

  275. </span></pre>
    276. 

  276. </div>
    277. 

  277. <h3>Regex Patterns</h3>
    278. 

  278. <p>You can also write a regular expression directly in the path instead of <code>:param</code>. Capture group values are available via <code>req.matches</code>, which is a <code>std::smatch</code>.</p>
    279. 

  279. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    280. 

  280. <span style="color:#747369;">// Only accept numeric IDs
    281. 

  281. </span><span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(</span><span style="color:#cc99cc;">R</span><span style="color:#d3d0c8;">&quot;(</span><span style="color:#99cc99;">/files/(\d+)</span><span style="color:#d3d0c8;">)&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    282. 

  282. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> id = req.</span><span style="color:#f2777a;">matches</span><span style="color:#d3d0c8;">[</span><span style="color:#f99157;">1</span><span style="color:#d3d0c8;">];  </span><span style="color:#747369;">// First capture group
    283. 

  283. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">File ID: </span><span style="color:#d3d0c8;">&quot; + </span><span style="color:#6699cc;">std::string</span><span style="color:#d3d0c8;">(id), &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    284. 

  284. </span><span style="color:#d3d0c8;">});
    285. 

  285. </span></pre>
    286. 

  286. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    287. 

  287. <span style="color:#a7adba;">// Only accept numeric IDs
    288. 

  288. </span><span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(</span><span style="color:#b48ead;">R</span><span style="color:#4f5b66;">&quot;(</span><span style="color:#a3be8c;">/files/(\d+)</span><span style="color:#4f5b66;">)&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    289. 

  289. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> id = req.</span><span style="color:#bf616a;">matches</span><span style="color:#4f5b66;">[</span><span style="color:#d08770;">1</span><span style="color:#4f5b66;">];  </span><span style="color:#a7adba;">// First capture group
    290. 

  290. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">File ID: </span><span style="color:#4f5b66;">&quot; + </span><span style="color:#8fa1b3;">std::string</span><span style="color:#4f5b66;">(id), &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    291. 

  291. </span><span style="color:#4f5b66;">});
    292. 

  292. </span></pre>
    293. 

  293. </div>
    294. 

  294. <p><code>/files/42</code> matches, but <code>/files/abc</code> doesn't. This is handy when you want to constrain what values are accepted.</p>
    295. 

  295. <h2>Building a Response</h2>
    296. 

  296. <p>The second parameter <code>res</code> is how you send data back to the client.</p>
    297. 

  297. <h3>Body and Content-Type</h3>
    298. 

  298. <p><code>res.set_content()</code> sets the body and Content-Type. That's all you need for a 200 response.</p>
    299. 

  299. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    300. 

  300. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/hi</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    301. 

  301. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">Hello!</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    302. 

  302. </span><span style="color:#d3d0c8;">});
    303. 

  303. </span></pre>
    304. 

  304. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    305. 

  305. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/hi</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    306. 

  306. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">Hello!</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    307. 

  307. </span><span style="color:#4f5b66;">});
    308. 

  308. </span></pre>
    309. 

  309. </div>
    310. 

  310. <h3>Status Code</h3>
    311. 

  311. <p>To return a different status code, assign to <code>res.status</code>.</p>
    312. 

  312. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    313. 

  313. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/not-found</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    314. 

  314. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#f2777a;">status </span><span style="color:#d3d0c8;">= </span><span style="color:#f99157;">404</span><span style="color:#d3d0c8;">;
    315. 

  315. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">Not found</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    316. 

  316. </span><span style="color:#d3d0c8;">});
    317. 

  317. </span></pre>
    318. 

  318. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    319. 

  319. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/not-found</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    320. 

  320. </span><span style="color:#4f5b66;">    res.</span><span style="color:#bf616a;">status </span><span style="color:#4f5b66;">= </span><span style="color:#d08770;">404</span><span style="color:#4f5b66;">;
    321. 

  321. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">Not found</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    322. 

  322. </span><span style="color:#4f5b66;">});
    323. 

  323. </span></pre>
    324. 

  324. </div>
    325. 

  325. <h3>Response Headers</h3>
    326. 

  326. <p>Add response headers with <code>res.set_header()</code>.</p>
    327. 

  327. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    328. 

  328. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/with-header</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    329. 

  329. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_header</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">X-Custom</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">my-value</span><span style="color:#d3d0c8;">&quot;);
    330. 

  330. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">Hello!</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    331. 

  331. </span><span style="color:#d3d0c8;">});
    332. 

  332. </span></pre>
    333. 

  333. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    334. 

  334. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/with-header</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    335. 

  335. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_header</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">X-Custom</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">my-value</span><span style="color:#4f5b66;">&quot;);
    336. 

  336. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">Hello!</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    337. 

  337. </span><span style="color:#4f5b66;">});
    338. 

  338. </span></pre>
    339. 

  339. </div>
    340. 

  340. <h2>Walking Through the Test Server</h2>
    341. 

  341. <p>Now let's use what we've learned to read through the test server from the previous chapter.</p>
    342. 

  342. <h3>GET /hi</h3>
    343. 

  343. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    344. 

  344. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/hi</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    345. 

  345. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">Hello!</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    346. 

  346. </span><span style="color:#d3d0c8;">});
    347. 

  347. </span></pre>
    348. 

  348. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    349. 

  349. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/hi</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    350. 

  350. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">Hello!</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    351. 

  351. </span><span style="color:#4f5b66;">});
    352. 

  352. </span></pre>
    353. 

  353. </div>
    354. 

  354. <p>The simplest possible handler. We don't need any information from the request, so the <code>req</code> parameter is left unnamed. It just returns <code>"Hello!"</code>.</p>
    355. 

  355. <h3>GET /search</h3>
    356. 

  356. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    357. 

  357. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/search</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    358. 

  358. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> q = req.</span><span style="color:#6699cc;">get_param_value</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">q</span><span style="color:#d3d0c8;">&quot;);
    359. 

  359. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">Query: </span><span style="color:#d3d0c8;">&quot; + q, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    360. 

  360. </span><span style="color:#d3d0c8;">});
    361. 

  361. </span></pre>
    362. 

  362. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    363. 

  363. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/search</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    364. 

  364. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> q = req.</span><span style="color:#8fa1b3;">get_param_value</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">q</span><span style="color:#4f5b66;">&quot;);
    365. 

  365. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">Query: </span><span style="color:#4f5b66;">&quot; + q, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    366. 

  366. </span><span style="color:#4f5b66;">});
    367. 

  367. </span></pre>
    368. 

  368. </div>
    369. 

  369. <p><code>req.get_param_value("q")</code> pulls out the query parameter <code>q</code>. A request to <code>/search?q=cpp-httplib</code> returns <code>"Query: cpp-httplib"</code>.</p>
    370. 

  370. <h3>POST /post</h3>
    371. 

  371. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    372. 

  372. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Post</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/post</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    373. 

  373. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(req.</span><span style="color:#f2777a;">body</span><span style="color:#d3d0c8;">, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    374. 

  374. </span><span style="color:#d3d0c8;">});
    375. 

  375. </span></pre>
    376. 

  376. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    377. 

  377. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Post</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/post</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    378. 

  378. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(req.</span><span style="color:#bf616a;">body</span><span style="color:#4f5b66;">, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    379. 

  379. </span><span style="color:#4f5b66;">});
    380. 

  380. </span></pre>
    381. 

  381. </div>
    382. 

  382. <p>An echo server. Whatever body the client sends, <code>req.body</code> holds it, and we send it straight back.</p>
    383. 

  383. <h3>POST /submit</h3>
    384. 

  384. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    385. 

  385. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Post</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/submit</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    386. 

  386. </span><span style="color:#d3d0c8;">    std::string result;
    387. 

  387. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">for </span><span style="color:#d3d0c8;">(</span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;[key, val] : req.</span><span style="color:#f2777a;">params</span><span style="color:#d3d0c8;">) {
    388. 

  388. </span><span style="color:#d3d0c8;">        result += key + &quot;</span><span style="color:#99cc99;"> = </span><span style="color:#d3d0c8;">&quot; + val + &quot;</span><span style="color:#66cccc;">\n</span><span style="color:#d3d0c8;">&quot;;
    389. 

  389. </span><span style="color:#d3d0c8;">    }
    390. 

  390. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(result, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    391. 

  391. </span><span style="color:#d3d0c8;">});
    392. 

  392. </span></pre>
    393. 

  393. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    394. 

  394. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Post</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/submit</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    395. 

  395. </span><span style="color:#4f5b66;">    std::string result;
    396. 

  396. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">for </span><span style="color:#4f5b66;">(</span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;[key, val] : req.</span><span style="color:#bf616a;">params</span><span style="color:#4f5b66;">) {
    397. 

  397. </span><span style="color:#4f5b66;">        result += key + &quot;</span><span style="color:#a3be8c;"> = </span><span style="color:#4f5b66;">&quot; + val + &quot;</span><span style="color:#96b5b4;">\n</span><span style="color:#4f5b66;">&quot;;
    398. 

  398. </span><span style="color:#4f5b66;">    }
    399. 

  399. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(result, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    400. 

  400. </span><span style="color:#4f5b66;">});
    401. 

  401. </span></pre>
    402. 

  402. </div>
    403. 

  403. <p>Loops over the form data in <code>req.params</code> using structured bindings (<code>auto &amp;[key, val]</code>) to unpack each key-value pair.</p>
    404. 

  404. <h3>POST /upload</h3>
    405. 

  405. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    406. 

  406. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Post</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/upload</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    407. 

  407. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> f = req.</span><span style="color:#f2777a;">form</span><span style="color:#d3d0c8;">.</span><span style="color:#6699cc;">get_file</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">file</span><span style="color:#d3d0c8;">&quot;);
    408. 

  408. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> content = f.</span><span style="color:#f2777a;">filename </span><span style="color:#d3d0c8;">+ &quot;</span><span style="color:#99cc99;"> (</span><span style="color:#d3d0c8;">&quot; + </span><span style="color:#6699cc;">std::to_string</span><span style="color:#d3d0c8;">(f.</span><span style="color:#f2777a;">content</span><span style="color:#d3d0c8;">.</span><span style="color:#6699cc;">size</span><span style="color:#d3d0c8;">()) + &quot;</span><span style="color:#99cc99;"> bytes)</span><span style="color:#d3d0c8;">&quot;;
    409. 

  409. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(content, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    410. 

  410. </span><span style="color:#d3d0c8;">});
    411. 

  411. </span></pre>
    412. 

  412. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    413. 

  413. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Post</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/upload</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    414. 

  414. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> f = req.</span><span style="color:#bf616a;">form</span><span style="color:#4f5b66;">.</span><span style="color:#8fa1b3;">get_file</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">file</span><span style="color:#4f5b66;">&quot;);
    415. 

  415. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> content = f.</span><span style="color:#bf616a;">filename </span><span style="color:#4f5b66;">+ &quot;</span><span style="color:#a3be8c;"> (</span><span style="color:#4f5b66;">&quot; + </span><span style="color:#8fa1b3;">std::to_string</span><span style="color:#4f5b66;">(f.</span><span style="color:#bf616a;">content</span><span style="color:#4f5b66;">.</span><span style="color:#8fa1b3;">size</span><span style="color:#4f5b66;">()) + &quot;</span><span style="color:#a3be8c;"> bytes)</span><span style="color:#4f5b66;">&quot;;
    416. 

  416. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(content, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    417. 

  417. </span><span style="color:#4f5b66;">});
    418. 

  418. </span></pre>
    419. 

  419. </div>
    420. 

  420. <p>Receives a file uploaded via multipart form data. <code>req.form.get_file("file")</code> fetches the field named <code>"file"</code>, and we respond with the filename and size.</p>
    421. 

  421. <h3>GET /users/:id</h3>
    422. 

  422. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    423. 

  423. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/users/:id</span><span style="color:#d3d0c8;">&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    424. 

  424. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> id = req.</span><span style="color:#f2777a;">path_params</span><span style="color:#d3d0c8;">.</span><span style="color:#6699cc;">at</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">id</span><span style="color:#d3d0c8;">&quot;);
    425. 

  425. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">User ID: </span><span style="color:#d3d0c8;">&quot; + id, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    426. 

  426. </span><span style="color:#d3d0c8;">});
    427. 

  427. </span></pre>
    428. 

  428. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    429. 

  429. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/users/:id</span><span style="color:#4f5b66;">&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    430. 

  430. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> id = req.</span><span style="color:#bf616a;">path_params</span><span style="color:#4f5b66;">.</span><span style="color:#8fa1b3;">at</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">id</span><span style="color:#4f5b66;">&quot;);
    431. 

  431. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">User ID: </span><span style="color:#4f5b66;">&quot; + id, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    432. 

  432. </span><span style="color:#4f5b66;">});
    433. 

  433. </span></pre>
    434. 

  434. </div>
    435. 

  435. <p><code>:id</code> is the path parameter. <code>req.path_params.at("id")</code> retrieves its value. <code>/users/42</code> gives you <code>"42"</code>, <code>/users/alice</code> gives you <code>"alice"</code>.</p>
    436. 

  436. <h3>GET /files/(\d+)</h3>
    437. 

  437. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    438. 

  438. <span style="color:#d3d0c8;">svr.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(</span><span style="color:#cc99cc;">R</span><span style="color:#d3d0c8;">&quot;(</span><span style="color:#99cc99;">/files/(\d+)</span><span style="color:#d3d0c8;">)&quot;, [](</span><span style="color:#cc99cc;">const auto </span><span style="color:#d3d0c8;">&amp;req, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    439. 

  439. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> id = req.</span><span style="color:#f2777a;">matches</span><span style="color:#d3d0c8;">[</span><span style="color:#f99157;">1</span><span style="color:#d3d0c8;">];
    440. 

  440. </span><span style="color:#d3d0c8;">    res.</span><span style="color:#6699cc;">set_content</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">File ID: </span><span style="color:#d3d0c8;">&quot; + </span><span style="color:#6699cc;">std::string</span><span style="color:#d3d0c8;">(id), &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    441. 

  441. </span><span style="color:#d3d0c8;">});
    442. 

  442. </span></pre>
    443. 

  443. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    444. 

  444. <span style="color:#4f5b66;">svr.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(</span><span style="color:#b48ead;">R</span><span style="color:#4f5b66;">&quot;(</span><span style="color:#a3be8c;">/files/(\d+)</span><span style="color:#4f5b66;">)&quot;, [](</span><span style="color:#b48ead;">const auto </span><span style="color:#4f5b66;">&amp;req, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    445. 

  445. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> id = req.</span><span style="color:#bf616a;">matches</span><span style="color:#4f5b66;">[</span><span style="color:#d08770;">1</span><span style="color:#4f5b66;">];
    446. 

  446. </span><span style="color:#4f5b66;">    res.</span><span style="color:#8fa1b3;">set_content</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">File ID: </span><span style="color:#4f5b66;">&quot; + </span><span style="color:#8fa1b3;">std::string</span><span style="color:#4f5b66;">(id), &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    447. 

  447. </span><span style="color:#4f5b66;">});
    448. 

  448. </span></pre>
    449. 

  449. </div>
    450. 

  450. <p>The regex <code>(\d+)</code> matches numeric IDs only. <code>/files/42</code> hits this handler, but <code>/files/abc</code> returns 404. <code>req.matches[1]</code> retrieves the first capture group.</p>
    451. 

  451. <h2>Next Steps</h2>
    452. 

  452. <p>You now have the full picture of how a server works. Routing, reading requests, building responses -- that's enough to build a real API server.</p>
    453. 

  453. <p>Next, let's look at serving static files. We'll build a server that delivers HTML and CSS.</p>
    454. 

  454. <p><strong>Next:</strong> <a href="../04-static-file-server">Static File Server</a></p>
    455. 

  455. 

  456.   </article>
    457. 

  457. </main>
    458. 

  458. 

  459.   </div>
    460. 

  460. 

  461.   <footer class="footer">
    462. 

  462.     &copy; 2026 yhirose. All rights reserved.
    463. 

  463.   </footer>
    464. 

  464. 

  465.   <script src="&#x2F;cpp-httplib/js/main.js"></script>
    466. 

  466. </body>
    467. 

  467. </html>
    468.