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    81. 

  81.     <h1>Basic Client</h1>
    82. 

  82.     <p>cpp-httplibはサーバーだけでなく、HTTPクライアント機能も備えています。<code>httplib::Client</code> を使って、GETやPOSTリクエストを送ってみましょう。</p>
    83. 

  83. <h2>テスト用サーバーの準備</h2>
    84. 

  84. <p>クライアントの動作を確認するために、リクエストを受け付けるサーバーを用意します。次のコードを保存し、前章と同じ手順でコンパイル・実行してください。サーバーの詳しい解説は次章で行います。</p>
    85. 

  85. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    86. 

  86. <span style="color:#cc99cc;">#include </span><span style="color:#d3d0c8;">&quot;</span><span style="color:#99cc99;">httplib.h</span><span style="color:#d3d0c8;">&quot;
    87. 

  87. </span><span style="color:#cc99cc;">#include </span><span style="color:#d3d0c8;">&lt;</span><span style="color:#99cc99;">iostream</span><span style="color:#d3d0c8;">&gt;
    88. 

  88. </span><span style="color:#d3d0c8;">
    89. 

  89. </span><span style="color:#cc99cc;">int </span><span style="color:#6699cc;">main</span><span style="color:#d3d0c8;">() {
    90. 

  90. </span><span style="color:#d3d0c8;">    httplib::Server svr;
    91. 

  91. </span><span style="color:#d3d0c8;">
    92. 

  92. </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 auto </span><span style="color:#d3d0c8;">&amp;, </span><span style="color:#cc99cc;">auto </span><span style="color:#d3d0c8;">&amp;res) {
    93. 

  93. </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;);
    94. 

  94. </span><span style="color:#d3d0c8;">    });
    95. 

  95. </span><span style="color:#d3d0c8;">
    96. 

  96. </span><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) {
    97. 

  97. </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;);
    98. 

  98. </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;);
    99. 

  99. </span><span style="color:#d3d0c8;">    });
    100. 

  100. </span><span style="color:#d3d0c8;">
    101. 

  101. </span><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) {
    102. 

  102. </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;);
    103. 

  103. </span><span style="color:#d3d0c8;">    });
    104. 

  104. </span><span style="color:#d3d0c8;">
    105. 

  105. </span><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) {
    106. 

  106. </span><span style="color:#d3d0c8;">        std::string result;
    107. 

  107. </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;">) {
    108. 

  108. </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;;
    109. 

  109. </span><span style="color:#d3d0c8;">        }
    110. 

  110. </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;);
    111. 

  111. </span><span style="color:#d3d0c8;">    });
    112. 

  112. </span><span style="color:#d3d0c8;">
    113. 

  113. </span><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) {
    114. 

  114. </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;);
    115. 

  115. </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;;
    116. 

  116. </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;);
    117. 

  117. </span><span style="color:#d3d0c8;">    });
    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;">/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) {
    120. 

  120. </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;);
    121. 

  121. </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;);
    122. 

  122. </span><span style="color:#d3d0c8;">    });
    123. 

  123. </span><span style="color:#d3d0c8;">
    124. 

  124. </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) {
    125. 

  125. </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;">];
    126. 

  126. </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;);
    127. 

  127. </span><span style="color:#d3d0c8;">    });
    128. 

  128. </span><span style="color:#d3d0c8;">
    129. 

  129. </span><span style="color:#d3d0c8;">    std::cout &lt;&lt; &quot;</span><span style="color:#99cc99;">Listening on port 8080...</span><span style="color:#d3d0c8;">&quot; &lt;&lt; std::endl;
    130. 

  130. </span><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;">);
    131. 

  131. </span><span style="color:#d3d0c8;">}
    132. 

  132. </span></pre>
    133. 

  133. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    134. 

  134. <span style="color:#b48ead;">#include </span><span style="color:#4f5b66;">&quot;</span><span style="color:#a3be8c;">httplib.h</span><span style="color:#4f5b66;">&quot;
    135. 

  135. </span><span style="color:#b48ead;">#include </span><span style="color:#4f5b66;">&lt;</span><span style="color:#a3be8c;">iostream</span><span style="color:#4f5b66;">&gt;
    136. 

  136. </span><span style="color:#4f5b66;">
    137. 

  137. </span><span style="color:#b48ead;">int </span><span style="color:#8fa1b3;">main</span><span style="color:#4f5b66;">() {
    138. 

  138. </span><span style="color:#4f5b66;">    httplib::Server svr;
    139. 

  139. </span><span style="color:#4f5b66;">
    140. 

  140. </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 auto </span><span style="color:#4f5b66;">&amp;, </span><span style="color:#b48ead;">auto </span><span style="color:#4f5b66;">&amp;res) {
    141. 

  141. </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;);
    142. 

  142. </span><span style="color:#4f5b66;">    });
    143. 

  143. </span><span style="color:#4f5b66;">
    144. 

  144. </span><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) {
    145. 

  145. </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;);
    146. 

  146. </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;);
    147. 

  147. </span><span style="color:#4f5b66;">    });
    148. 

  148. </span><span style="color:#4f5b66;">
    149. 

  149. </span><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) {
    150. 

  150. </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;);
    151. 

  151. </span><span style="color:#4f5b66;">    });
    152. 

  152. </span><span style="color:#4f5b66;">
    153. 

  153. </span><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) {
    154. 

  154. </span><span style="color:#4f5b66;">        std::string result;
    155. 

  155. </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;">) {
    156. 

  156. </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;;
    157. 

  157. </span><span style="color:#4f5b66;">        }
    158. 

  158. </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;);
    159. 

  159. </span><span style="color:#4f5b66;">    });
    160. 

  160. </span><span style="color:#4f5b66;">
    161. 

  161. </span><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) {
    162. 

  162. </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;);
    163. 

  163. </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;;
    164. 

  164. </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;);
    165. 

  165. </span><span style="color:#4f5b66;">    });
    166. 

  166. </span><span style="color:#4f5b66;">
    167. 

  167. </span><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) {
    168. 

  168. </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;);
    169. 

  169. </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;);
    170. 

  170. </span><span style="color:#4f5b66;">    });
    171. 

  171. </span><span style="color:#4f5b66;">
    172. 

  172. </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) {
    173. 

  173. </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;">];
    174. 

  174. </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;);
    175. 

  175. </span><span style="color:#4f5b66;">    });
    176. 

  176. </span><span style="color:#4f5b66;">
    177. 

  177. </span><span style="color:#4f5b66;">    std::cout &lt;&lt; &quot;</span><span style="color:#a3be8c;">Listening on port 8080...</span><span style="color:#4f5b66;">&quot; &lt;&lt; std::endl;
    178. 

  178. </span><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;">);
    179. 

  179. </span><span style="color:#4f5b66;">}
    180. 

  180. </span></pre>
    181. 

  181. </div>
    182. 

  182. <h2>GETリクエスト</h2>
    183. 

  183. <p>サーバーが起動したら、別のターミナルを開いて試してみましょう。まず、最もシンプルなGETリクエストです。</p>
    184. 

  184. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    185. 

  185. <span style="color:#cc99cc;">#include </span><span style="color:#d3d0c8;">&quot;</span><span style="color:#99cc99;">httplib.h</span><span style="color:#d3d0c8;">&quot;
    186. 

  186. </span><span style="color:#cc99cc;">#include </span><span style="color:#d3d0c8;">&lt;</span><span style="color:#99cc99;">iostream</span><span style="color:#d3d0c8;">&gt;
    187. 

  187. </span><span style="color:#d3d0c8;">
    188. 

  188. </span><span style="color:#cc99cc;">int </span><span style="color:#6699cc;">main</span><span style="color:#d3d0c8;">() {
    189. 

  189. </span><span style="color:#d3d0c8;">    httplib::Client </span><span style="color:#6699cc;">cli</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">http://localhost:8080</span><span style="color:#d3d0c8;">&quot;);
    190. 

  190. </span><span style="color:#d3d0c8;">
    191. 

  191. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> res = cli.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/hi</span><span style="color:#d3d0c8;">&quot;);
    192. 

  192. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">if </span><span style="color:#d3d0c8;">(res) {
    193. 

  193. </span><span style="color:#d3d0c8;">        std::cout &lt;&lt; res-&gt;</span><span style="color:#f2777a;">status </span><span style="color:#d3d0c8;">&lt;&lt; std::endl;  </span><span style="color:#747369;">// 200
    194. 

  194. </span><span style="color:#d3d0c8;">        std::cout &lt;&lt; res-&gt;</span><span style="color:#f2777a;">body </span><span style="color:#d3d0c8;">&lt;&lt; std::endl;    </span><span style="color:#747369;">// Hello!
    195. 

  195. </span><span style="color:#d3d0c8;">    }
    196. 

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

  197. </span></pre>
    198. 

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

  199. <span style="color:#b48ead;">#include </span><span style="color:#4f5b66;">&quot;</span><span style="color:#a3be8c;">httplib.h</span><span style="color:#4f5b66;">&quot;
    200. 

  200. </span><span style="color:#b48ead;">#include </span><span style="color:#4f5b66;">&lt;</span><span style="color:#a3be8c;">iostream</span><span style="color:#4f5b66;">&gt;
    201. 

  201. </span><span style="color:#4f5b66;">
    202. 

  202. </span><span style="color:#b48ead;">int </span><span style="color:#8fa1b3;">main</span><span style="color:#4f5b66;">() {
    203. 

  203. </span><span style="color:#4f5b66;">    httplib::Client </span><span style="color:#8fa1b3;">cli</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">http://localhost:8080</span><span style="color:#4f5b66;">&quot;);
    204. 

  204. </span><span style="color:#4f5b66;">
    205. 

  205. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> res = cli.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/hi</span><span style="color:#4f5b66;">&quot;);
    206. 

  206. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">if </span><span style="color:#4f5b66;">(res) {
    207. 

  207. </span><span style="color:#4f5b66;">        std::cout &lt;&lt; res-&gt;</span><span style="color:#bf616a;">status </span><span style="color:#4f5b66;">&lt;&lt; std::endl;  </span><span style="color:#a7adba;">// 200
    208. 

  208. </span><span style="color:#4f5b66;">        std::cout &lt;&lt; res-&gt;</span><span style="color:#bf616a;">body </span><span style="color:#4f5b66;">&lt;&lt; std::endl;    </span><span style="color:#a7adba;">// Hello!
    209. 

  209. </span><span style="color:#4f5b66;">    }
    210. 

  210. </span><span style="color:#4f5b66;">}
    211. 

  211. </span></pre>
    212. 

  212. </div>
    213. 

  213. <p><code>httplib::Client</code> のコンストラクターにサーバーのアドレスを渡し、<code>Get()</code> でリクエストを送ります。戻り値の <code>res</code> からステータスコードやボディを取得できます。</p>
    214. 

  214. <p>対応する <code>curl</code> コマンドはこうなります。</p>
    215. 

  215. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    216. 

  216. <span style="color:#6699cc;">curl</span><span style="color:#d3d0c8;"> http://localhost:8080/hi
    217. 

  217. </span><span style="color:#747369;"># Hello!
    218. 

  218. </span></pre>
    219. 

  219. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    220. 

  220. <span style="color:#8fa1b3;">curl</span><span style="color:#4f5b66;"> http://localhost:8080/hi
    221. 

  221. </span><span style="color:#a7adba;"># Hello!
    222. 

  222. </span></pre>
    223. 

  223. </div>
    224. 

  224. <h2>レスポンスの確認</h2>
    225. 

  225. <p>レスポンスには、ステータスコードとボディ以外にもヘッダー情報が含まれています。</p>
    226. 

  226. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    227. 

  227. <span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> res = cli.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/hi</span><span style="color:#d3d0c8;">&quot;);
    228. 

  228. </span><span style="color:#cc99cc;">if </span><span style="color:#d3d0c8;">(res) {
    229. 

  229. </span><span style="color:#d3d0c8;">    </span><span style="color:#747369;">// ステータスコード
    230. 

  230. </span><span style="color:#d3d0c8;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#f2777a;">status </span><span style="color:#d3d0c8;">&lt;&lt; std::endl;  </span><span style="color:#747369;">// 200
    231. 

  231. </span><span style="color:#d3d0c8;">
    232. 

  232. </span><span style="color:#d3d0c8;">    </span><span style="color:#747369;">// ボディ
    233. 

  233. </span><span style="color:#d3d0c8;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#f2777a;">body </span><span style="color:#d3d0c8;">&lt;&lt; std::endl;  </span><span style="color:#747369;">// Hello!
    234. 

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

  235. </span><span style="color:#d3d0c8;">    </span><span style="color:#747369;">// ヘッダー
    236. 

  236. </span><span style="color:#d3d0c8;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#6699cc;">get_header_value</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">Content-Type</span><span style="color:#d3d0c8;">&quot;) &lt;&lt; std::endl;  </span><span style="color:#747369;">// text/plain
    237. 

  237. </span><span style="color:#d3d0c8;">}
    238. 

  238. </span></pre>
    239. 

  239. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    240. 

  240. <span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> res = cli.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/hi</span><span style="color:#4f5b66;">&quot;);
    241. 

  241. </span><span style="color:#b48ead;">if </span><span style="color:#4f5b66;">(res) {
    242. 

  242. </span><span style="color:#4f5b66;">    </span><span style="color:#a7adba;">// ステータスコード
    243. 

  243. </span><span style="color:#4f5b66;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#bf616a;">status </span><span style="color:#4f5b66;">&lt;&lt; std::endl;  </span><span style="color:#a7adba;">// 200
    244. 

  244. </span><span style="color:#4f5b66;">
    245. 

  245. </span><span style="color:#4f5b66;">    </span><span style="color:#a7adba;">// ボディ
    246. 

  246. </span><span style="color:#4f5b66;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#bf616a;">body </span><span style="color:#4f5b66;">&lt;&lt; std::endl;  </span><span style="color:#a7adba;">// Hello!
    247. 

  247. </span><span style="color:#4f5b66;">
    248. 

  248. </span><span style="color:#4f5b66;">    </span><span style="color:#a7adba;">// ヘッダー
    249. 

  249. </span><span style="color:#4f5b66;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#8fa1b3;">get_header_value</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">Content-Type</span><span style="color:#4f5b66;">&quot;) &lt;&lt; std::endl;  </span><span style="color:#a7adba;">// text/plain
    250. 

  250. </span><span style="color:#4f5b66;">}
    251. 

  251. </span></pre>
    252. 

  252. </div>
    253. 

  253. <p><code>res-&gt;body</code> は <code>std::string</code> なので、JSON レスポンスをパースしたい場合は <a href="https://github.com/nlohmann/json">nlohmann/json</a> などの JSON ライブラリにそのまま渡せます。</p>
    254. 

  254. <h2>クエリパラメーター</h2>
    255. 

  255. <p>GETリクエストにクエリパラメーターを付けるには、URLに直接書くか、<code>httplib::Params</code> を使います。</p>
    256. 

  256. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    257. 

  257. <span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> res = cli.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/search</span><span style="color:#d3d0c8;">&quot;, httplib::Params{{&quot;</span><span style="color:#99cc99;">q</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">cpp-httplib</span><span style="color:#d3d0c8;">&quot;}});
    258. 

  258. </span><span style="color:#cc99cc;">if </span><span style="color:#d3d0c8;">(res) {
    259. 

  259. </span><span style="color:#d3d0c8;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#f2777a;">body </span><span style="color:#d3d0c8;">&lt;&lt; std::endl;  </span><span style="color:#747369;">// Query: cpp-httplib
    260. 

  260. </span><span style="color:#d3d0c8;">}
    261. 

  261. </span></pre>
    262. 

  262. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    263. 

  263. <span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> res = cli.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/search</span><span style="color:#4f5b66;">&quot;, httplib::Params{{&quot;</span><span style="color:#a3be8c;">q</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">cpp-httplib</span><span style="color:#4f5b66;">&quot;}});
    264. 

  264. </span><span style="color:#b48ead;">if </span><span style="color:#4f5b66;">(res) {
    265. 

  265. </span><span style="color:#4f5b66;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#bf616a;">body </span><span style="color:#4f5b66;">&lt;&lt; std::endl;  </span><span style="color:#a7adba;">// Query: cpp-httplib
    266. 

  266. </span><span style="color:#4f5b66;">}
    267. 

  267. </span></pre>
    268. 

  268. </div>
    269. 

  269. <p><code>httplib::Params</code> を使うと、特殊文字のURLエンコードを自動で行ってくれます。</p>
    270. 

  270. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    271. 

  271. <span style="color:#6699cc;">curl </span><span style="color:#d3d0c8;">&quot;</span><span style="color:#99cc99;">http://localhost:8080/search?q=cpp-httplib</span><span style="color:#d3d0c8;">&quot;
    272. 

  272. </span><span style="color:#747369;"># Query: cpp-httplib
    273. 

  273. </span></pre>
    274. 

  274. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    275. 

  275. <span style="color:#8fa1b3;">curl </span><span style="color:#4f5b66;">&quot;</span><span style="color:#a3be8c;">http://localhost:8080/search?q=cpp-httplib</span><span style="color:#4f5b66;">&quot;
    276. 

  276. </span><span style="color:#a7adba;"># Query: cpp-httplib
    277. 

  277. </span></pre>
    278. 

  278. </div>
    279. 

  279. <h2>パスパラメーター</h2>
    280. 

  280. <p>URLのパスに値を直接埋め込む場合も、クライアント側は特別なAPIは不要です。パスをそのまま <code>Get()</code> に渡すだけです。</p>
    281. 

  281. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    282. 

  282. <span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> res = cli.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/users/42</span><span style="color:#d3d0c8;">&quot;);
    283. 

  283. </span><span style="color:#cc99cc;">if </span><span style="color:#d3d0c8;">(res) {
    284. 

  284. </span><span style="color:#d3d0c8;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#f2777a;">body </span><span style="color:#d3d0c8;">&lt;&lt; std::endl;  </span><span style="color:#747369;">// User ID: 42
    285. 

  285. </span><span style="color:#d3d0c8;">}
    286. 

  286. </span></pre>
    287. 

  287. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    288. 

  288. <span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> res = cli.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/users/42</span><span style="color:#4f5b66;">&quot;);
    289. 

  289. </span><span style="color:#b48ead;">if </span><span style="color:#4f5b66;">(res) {
    290. 

  290. </span><span style="color:#4f5b66;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#bf616a;">body </span><span style="color:#4f5b66;">&lt;&lt; std::endl;  </span><span style="color:#a7adba;">// User ID: 42
    291. 

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

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

  293. </div><div class="code-dark"><pre style="background-color:#2d2d2d;">
    294. 

  294. <span style="color:#6699cc;">curl</span><span style="color:#d3d0c8;"> http://localhost:8080/users/42
    295. 

  295. </span><span style="color:#747369;"># User ID: 42
    296. 

  296. </span></pre>
    297. 

  297. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    298. 

  298. <span style="color:#8fa1b3;">curl</span><span style="color:#4f5b66;"> http://localhost:8080/users/42
    299. 

  299. </span><span style="color:#a7adba;"># User ID: 42
    300. 

  300. </span></pre>
    301. 

  301. </div>
    302. 

  302. <p>テスト用サーバーには、正規表現でIDを数字のみに絞った <code>/files/(\d+)</code> もあります。</p>
    303. 

  303. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    304. 

  304. <span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> res = cli.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/files/42</span><span style="color:#d3d0c8;">&quot;);
    305. 

  305. </span><span style="color:#cc99cc;">if </span><span style="color:#d3d0c8;">(res) {
    306. 

  306. </span><span style="color:#d3d0c8;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#f2777a;">body </span><span style="color:#d3d0c8;">&lt;&lt; std::endl;  </span><span style="color:#747369;">// File ID: 42
    307. 

  307. </span><span style="color:#d3d0c8;">}
    308. 

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

  309. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    310. 

  310. <span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> res = cli.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/files/42</span><span style="color:#4f5b66;">&quot;);
    311. 

  311. </span><span style="color:#b48ead;">if </span><span style="color:#4f5b66;">(res) {
    312. 

  312. </span><span style="color:#4f5b66;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#bf616a;">body </span><span style="color:#4f5b66;">&lt;&lt; std::endl;  </span><span style="color:#a7adba;">// File ID: 42
    313. 

  313. </span><span style="color:#4f5b66;">}
    314. 

  314. </span></pre>
    315. 

  315. </div><div class="code-dark"><pre style="background-color:#2d2d2d;">
    316. 

  316. <span style="color:#6699cc;">curl</span><span style="color:#d3d0c8;"> http://localhost:8080/files/42
    317. 

  317. </span><span style="color:#747369;"># File ID: 42
    318. 

  318. </span></pre>
    319. 

  319. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    320. 

  320. <span style="color:#8fa1b3;">curl</span><span style="color:#4f5b66;"> http://localhost:8080/files/42
    321. 

  321. </span><span style="color:#a7adba;"># File ID: 42
    322. 

  322. </span></pre>
    323. 

  323. </div>
    324. 

  324. <p><code>/files/abc</code> のように数字以外を渡すと404が返ります。仕組みは次章で解説します。</p>
    325. 

  325. <h2>リクエストヘッダー</h2>
    326. 

  326. <p>カスタムHTTPヘッダーを付けるには、<code>httplib::Headers</code> を渡します。<code>Get()</code> や <code>Post()</code> のどちらでも使えます。</p>
    327. 

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

  328. <span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> res = cli.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/hi</span><span style="color:#d3d0c8;">&quot;, httplib::Headers{
    329. 

  329. </span><span style="color:#d3d0c8;">    {&quot;</span><span style="color:#99cc99;">Authorization</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">Bearer my-token</span><span style="color:#d3d0c8;">&quot;}
    330. 

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

  331. </span></pre>
    332. 

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

  333. <span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> res = cli.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/hi</span><span style="color:#4f5b66;">&quot;, httplib::Headers{
    334. 

  334. </span><span style="color:#4f5b66;">    {&quot;</span><span style="color:#a3be8c;">Authorization</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">Bearer my-token</span><span style="color:#4f5b66;">&quot;}
    335. 

  335. </span><span style="color:#4f5b66;">});
    336. 

  336. </span></pre>
    337. 

  337. </div><div class="code-dark"><pre style="background-color:#2d2d2d;">
    338. 

  338. <span style="color:#6699cc;">curl</span><span style="color:#f2777a;"> -H </span><span style="color:#d3d0c8;">&quot;</span><span style="color:#99cc99;">Authorization: Bearer my-token</span><span style="color:#d3d0c8;">&quot; http://localhost:8080/hi
    339. 

  339. </span></pre>
    340. 

  340. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    341. 

  341. <span style="color:#8fa1b3;">curl</span><span style="color:#bf616a;"> -H </span><span style="color:#4f5b66;">&quot;</span><span style="color:#a3be8c;">Authorization: Bearer my-token</span><span style="color:#4f5b66;">&quot; http://localhost:8080/hi
    342. 

  342. </span></pre>
    343. 

  343. </div>
    344. 

  344. <h2>POSTリクエスト</h2>
    345. 

  345. <p>テキストデータをPOSTしてみましょう。<code>Post()</code> の第2引数にボディ、第3引数にContent-Typeを指定します。</p>
    346. 

  346. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    347. 

  347. <span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> res = cli.</span><span style="color:#6699cc;">Post</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/post</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">Hello, Server!</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;);
    348. 

  348. </span><span style="color:#cc99cc;">if </span><span style="color:#d3d0c8;">(res) {
    349. 

  349. </span><span style="color:#d3d0c8;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#f2777a;">status </span><span style="color:#d3d0c8;">&lt;&lt; std::endl;  </span><span style="color:#747369;">// 200
    350. 

  350. </span><span style="color:#d3d0c8;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#f2777a;">body </span><span style="color:#d3d0c8;">&lt;&lt; std::endl;    </span><span style="color:#747369;">// Hello, Server!
    351. 

  351. </span><span style="color:#d3d0c8;">}
    352. 

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

  353. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    354. 

  354. <span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> res = cli.</span><span style="color:#8fa1b3;">Post</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/post</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">Hello, Server!</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;);
    355. 

  355. </span><span style="color:#b48ead;">if </span><span style="color:#4f5b66;">(res) {
    356. 

  356. </span><span style="color:#4f5b66;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#bf616a;">status </span><span style="color:#4f5b66;">&lt;&lt; std::endl;  </span><span style="color:#a7adba;">// 200
    357. 

  357. </span><span style="color:#4f5b66;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#bf616a;">body </span><span style="color:#4f5b66;">&lt;&lt; std::endl;    </span><span style="color:#a7adba;">// Hello, Server!
    358. 

  358. </span><span style="color:#4f5b66;">}
    359. 

  359. </span></pre>
    360. 

  360. </div>
    361. 

  361. <p>テスト用サーバーの <code>/post</code> はボディをそのまま返すので、送った文字列がそのまま返ってきます。</p>
    362. 

  362. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    363. 

  363. <span style="color:#6699cc;">curl</span><span style="color:#f2777a;"> -X</span><span style="color:#d3d0c8;"> POST</span><span style="color:#f2777a;"> -H </span><span style="color:#d3d0c8;">&quot;</span><span style="color:#99cc99;">Content-Type: text/plain</span><span style="color:#d3d0c8;">&quot;</span><span style="color:#f2777a;"> -d </span><span style="color:#d3d0c8;">&quot;</span><span style="color:#99cc99;">Hello, Server!</span><span style="color:#d3d0c8;">&quot; http://localhost:8080/post
    364. 

  364. </span><span style="color:#747369;"># Hello, Server!
    365. 

  365. </span></pre>
    366. 

  366. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    367. 

  367. <span style="color:#8fa1b3;">curl</span><span style="color:#bf616a;"> -X</span><span style="color:#4f5b66;"> POST</span><span style="color:#bf616a;"> -H </span><span style="color:#4f5b66;">&quot;</span><span style="color:#a3be8c;">Content-Type: text/plain</span><span style="color:#4f5b66;">&quot;</span><span style="color:#bf616a;"> -d </span><span style="color:#4f5b66;">&quot;</span><span style="color:#a3be8c;">Hello, Server!</span><span style="color:#4f5b66;">&quot; http://localhost:8080/post
    368. 

  368. </span><span style="color:#a7adba;"># Hello, Server!
    369. 

  369. </span></pre>
    370. 

  370. </div>
    371. 

  371. <h2>フォームデータの送信</h2>
    372. 

  372. <p>HTMLフォームのように、キーと値のペアを送ることもできます。<code>httplib::Params</code> を使います。</p>
    373. 

  373. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    374. 

  374. <span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> res = cli.</span><span style="color:#6699cc;">Post</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/submit</span><span style="color:#d3d0c8;">&quot;, httplib::Params{
    375. 

  375. </span><span style="color:#d3d0c8;">    {&quot;</span><span style="color:#99cc99;">name</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">Alice</span><span style="color:#d3d0c8;">&quot;},
    376. 

  376. </span><span style="color:#d3d0c8;">    {&quot;</span><span style="color:#99cc99;">age</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">30</span><span style="color:#d3d0c8;">&quot;}
    377. 

  377. </span><span style="color:#d3d0c8;">});
    378. 

  378. </span><span style="color:#cc99cc;">if </span><span style="color:#d3d0c8;">(res) {
    379. 

  379. </span><span style="color:#d3d0c8;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#f2777a;">body </span><span style="color:#d3d0c8;">&lt;&lt; std::endl;
    380. 

  380. </span><span style="color:#d3d0c8;">    </span><span style="color:#747369;">// age = 30
    381. 

  381. </span><span style="color:#d3d0c8;">    </span><span style="color:#747369;">// name = Alice
    382. 

  382. </span><span style="color:#d3d0c8;">}
    383. 

  383. </span></pre>
    384. 

  384. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    385. 

  385. <span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> res = cli.</span><span style="color:#8fa1b3;">Post</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/submit</span><span style="color:#4f5b66;">&quot;, httplib::Params{
    386. 

  386. </span><span style="color:#4f5b66;">    {&quot;</span><span style="color:#a3be8c;">name</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">Alice</span><span style="color:#4f5b66;">&quot;},
    387. 

  387. </span><span style="color:#4f5b66;">    {&quot;</span><span style="color:#a3be8c;">age</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">30</span><span style="color:#4f5b66;">&quot;}
    388. 

  388. </span><span style="color:#4f5b66;">});
    389. 

  389. </span><span style="color:#b48ead;">if </span><span style="color:#4f5b66;">(res) {
    390. 

  390. </span><span style="color:#4f5b66;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#bf616a;">body </span><span style="color:#4f5b66;">&lt;&lt; std::endl;
    391. 

  391. </span><span style="color:#4f5b66;">    </span><span style="color:#a7adba;">// age = 30
    392. 

  392. </span><span style="color:#4f5b66;">    </span><span style="color:#a7adba;">// name = Alice
    393. 

  393. </span><span style="color:#4f5b66;">}
    394. 

  394. </span></pre>
    395. 

  395. </div>
    396. 

  396. <p>これは <code>application/x-www-form-urlencoded</code> 形式で送信されます。</p>
    397. 

  397. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    398. 

  398. <span style="color:#6699cc;">curl</span><span style="color:#f2777a;"> -X</span><span style="color:#d3d0c8;"> POST</span><span style="color:#f2777a;"> -d </span><span style="color:#d3d0c8;">&quot;</span><span style="color:#99cc99;">name=Alice&amp;age=30</span><span style="color:#d3d0c8;">&quot; http://localhost:8080/submit
    399. 

  399. </span></pre>
    400. 

  400. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    401. 

  401. <span style="color:#8fa1b3;">curl</span><span style="color:#bf616a;"> -X</span><span style="color:#4f5b66;"> POST</span><span style="color:#bf616a;"> -d </span><span style="color:#4f5b66;">&quot;</span><span style="color:#a3be8c;">name=Alice&amp;age=30</span><span style="color:#4f5b66;">&quot; http://localhost:8080/submit
    402. 

  402. </span></pre>
    403. 

  403. </div>
    404. 

  404. <h2>ファイルのPOST</h2>
    405. 

  405. <p>ファイルをアップロードするには、<code>httplib::UploadFormDataItems</code> を使ってマルチパートフォームデータとして送信します。</p>
    406. 

  406. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    407. 

  407. <span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> res = cli.</span><span style="color:#6699cc;">Post</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/upload</span><span style="color:#d3d0c8;">&quot;, httplib::UploadFormDataItems{
    408. 

  408. </span><span style="color:#d3d0c8;">    {&quot;</span><span style="color:#99cc99;">file</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">Hello, File!</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">hello.txt</span><span style="color:#d3d0c8;">&quot;, &quot;</span><span style="color:#99cc99;">text/plain</span><span style="color:#d3d0c8;">&quot;}
    409. 

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

  410. </span><span style="color:#cc99cc;">if </span><span style="color:#d3d0c8;">(res) {
    411. 

  411. </span><span style="color:#d3d0c8;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#f2777a;">body </span><span style="color:#d3d0c8;">&lt;&lt; std::endl;  </span><span style="color:#747369;">// hello.txt (12 bytes)
    412. 

  412. </span><span style="color:#d3d0c8;">}
    413. 

  413. </span></pre>
    414. 

  414. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    415. 

  415. <span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> res = cli.</span><span style="color:#8fa1b3;">Post</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/upload</span><span style="color:#4f5b66;">&quot;, httplib::UploadFormDataItems{
    416. 

  416. </span><span style="color:#4f5b66;">    {&quot;</span><span style="color:#a3be8c;">file</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">Hello, File!</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">hello.txt</span><span style="color:#4f5b66;">&quot;, &quot;</span><span style="color:#a3be8c;">text/plain</span><span style="color:#4f5b66;">&quot;}
    417. 

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

  418. </span><span style="color:#b48ead;">if </span><span style="color:#4f5b66;">(res) {
    419. 

  419. </span><span style="color:#4f5b66;">    std::cout &lt;&lt; res-&gt;</span><span style="color:#bf616a;">body </span><span style="color:#4f5b66;">&lt;&lt; std::endl;  </span><span style="color:#a7adba;">// hello.txt (12 bytes)
    420. 

  420. </span><span style="color:#4f5b66;">}
    421. 

  421. </span></pre>
    422. 

  422. </div>
    423. 

  423. <p><code>UploadFormDataItems</code> の各要素は <code>{name, content, filename, content_type}</code> の4つのフィールドで構成されます。</p>
    424. 

  424. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    425. 

  425. <span style="color:#6699cc;">curl</span><span style="color:#f2777a;"> -F </span><span style="color:#d3d0c8;">&quot;</span><span style="color:#99cc99;">file=Hello, File!;filename=hello.txt;type=text/plain</span><span style="color:#d3d0c8;">&quot; http://localhost:8080/upload
    426. 

  426. </span></pre>
    427. 

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

  428. <span style="color:#8fa1b3;">curl</span><span style="color:#bf616a;"> -F </span><span style="color:#4f5b66;">&quot;</span><span style="color:#a3be8c;">file=Hello, File!;filename=hello.txt;type=text/plain</span><span style="color:#4f5b66;">&quot; http://localhost:8080/upload
    429. 

  429. </span></pre>
    430. 

  430. </div>
    431. 

  431. <h2>エラーハンドリング</h2>
    432. 

  432. <p>ネットワーク通信では、サーバーに接続できない場合があります。<code>res</code> が有効かどうかを必ず確認しましょう。</p>
    433. 

  433. <div class="code-dark"><pre style="background-color:#2d2d2d;">
    434. 

  434. <span style="color:#d3d0c8;">httplib::Client </span><span style="color:#6699cc;">cli</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">http://localhost:9999</span><span style="color:#d3d0c8;">&quot;);  </span><span style="color:#747369;">// 存在しないポート
    435. 

  435. </span><span style="color:#cc99cc;">auto</span><span style="color:#d3d0c8;"> res = cli.</span><span style="color:#6699cc;">Get</span><span style="color:#d3d0c8;">(&quot;</span><span style="color:#99cc99;">/hi</span><span style="color:#d3d0c8;">&quot;);
    436. 

  436. </span><span style="color:#d3d0c8;">
    437. 

  437. </span><span style="color:#cc99cc;">if </span><span style="color:#d3d0c8;">(!res) {
    438. 

  438. </span><span style="color:#d3d0c8;">    </span><span style="color:#747369;">// 接続エラー
    439. 

  439. </span><span style="color:#d3d0c8;">    std::cout &lt;&lt; &quot;</span><span style="color:#99cc99;">Error: </span><span style="color:#d3d0c8;">&quot; &lt;&lt; </span><span style="color:#6699cc;">httplib::to_string</span><span style="color:#d3d0c8;">(res.</span><span style="color:#6699cc;">error</span><span style="color:#d3d0c8;">()) &lt;&lt; std::endl;
    440. 

  440. </span><span style="color:#d3d0c8;">    </span><span style="color:#747369;">// Error: Connection
    441. 

  441. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">return </span><span style="color:#f99157;">1</span><span style="color:#d3d0c8;">;
    442. 

  442. </span><span style="color:#d3d0c8;">}
    443. 

  443. </span><span style="color:#d3d0c8;">
    444. 

  444. </span><span style="color:#747369;">// ここに到達すればレスポンスを受信できている
    445. 

  445. </span><span style="color:#cc99cc;">if </span><span style="color:#d3d0c8;">(res-&gt;</span><span style="color:#f2777a;">status </span><span style="color:#d3d0c8;">!= </span><span style="color:#f99157;">200</span><span style="color:#d3d0c8;">) {
    446. 

  446. </span><span style="color:#d3d0c8;">    std::cout &lt;&lt; &quot;</span><span style="color:#99cc99;">HTTP Error: </span><span style="color:#d3d0c8;">&quot; &lt;&lt; res-&gt;</span><span style="color:#f2777a;">status </span><span style="color:#d3d0c8;">&lt;&lt; std::endl;
    447. 

  447. </span><span style="color:#d3d0c8;">    </span><span style="color:#cc99cc;">return </span><span style="color:#f99157;">1</span><span style="color:#d3d0c8;">;
    448. 

  448. </span><span style="color:#d3d0c8;">}
    449. 

  449. </span><span style="color:#d3d0c8;">
    450. 

  450. </span><span style="color:#d3d0c8;">std::cout &lt;&lt; res-&gt;</span><span style="color:#f2777a;">body </span><span style="color:#d3d0c8;">&lt;&lt; std::endl;
    451. 

  451. </span></pre>
    452. 

  452. </div><div class="code-light"><pre style="background-color:#eff1f5;">
    453. 

  453. <span style="color:#4f5b66;">httplib::Client </span><span style="color:#8fa1b3;">cli</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">http://localhost:9999</span><span style="color:#4f5b66;">&quot;);  </span><span style="color:#a7adba;">// 存在しないポート
    454. 

  454. </span><span style="color:#b48ead;">auto</span><span style="color:#4f5b66;"> res = cli.</span><span style="color:#8fa1b3;">Get</span><span style="color:#4f5b66;">(&quot;</span><span style="color:#a3be8c;">/hi</span><span style="color:#4f5b66;">&quot;);
    455. 

  455. </span><span style="color:#4f5b66;">
    456. 

  456. </span><span style="color:#b48ead;">if </span><span style="color:#4f5b66;">(!res) {
    457. 

  457. </span><span style="color:#4f5b66;">    </span><span style="color:#a7adba;">// 接続エラー
    458. 

  458. </span><span style="color:#4f5b66;">    std::cout &lt;&lt; &quot;</span><span style="color:#a3be8c;">Error: </span><span style="color:#4f5b66;">&quot; &lt;&lt; </span><span style="color:#8fa1b3;">httplib::to_string</span><span style="color:#4f5b66;">(res.</span><span style="color:#8fa1b3;">error</span><span style="color:#4f5b66;">()) &lt;&lt; std::endl;
    459. 

  459. </span><span style="color:#4f5b66;">    </span><span style="color:#a7adba;">// Error: Connection
    460. 

  460. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">return </span><span style="color:#d08770;">1</span><span style="color:#4f5b66;">;
    461. 

  461. </span><span style="color:#4f5b66;">}
    462. 

  462. </span><span style="color:#4f5b66;">
    463. 

  463. </span><span style="color:#a7adba;">// ここに到達すればレスポンスを受信できている
    464. 

  464. </span><span style="color:#b48ead;">if </span><span style="color:#4f5b66;">(res-&gt;</span><span style="color:#bf616a;">status </span><span style="color:#4f5b66;">!= </span><span style="color:#d08770;">200</span><span style="color:#4f5b66;">) {
    465. 

  465. </span><span style="color:#4f5b66;">    std::cout &lt;&lt; &quot;</span><span style="color:#a3be8c;">HTTP Error: </span><span style="color:#4f5b66;">&quot; &lt;&lt; res-&gt;</span><span style="color:#bf616a;">status </span><span style="color:#4f5b66;">&lt;&lt; std::endl;
    466. 

  466. </span><span style="color:#4f5b66;">    </span><span style="color:#b48ead;">return </span><span style="color:#d08770;">1</span><span style="color:#4f5b66;">;
    467. 

  467. </span><span style="color:#4f5b66;">}
    468. 

  468. </span><span style="color:#4f5b66;">
    469. 

  469. </span><span style="color:#4f5b66;">std::cout &lt;&lt; res-&gt;</span><span style="color:#bf616a;">body </span><span style="color:#4f5b66;">&lt;&lt; std::endl;
    470. 

  470. </span></pre>
    471. 

  471. </div>
    472. 

  472. <p>エラーには2つのレベルがあります。</p>
    473. 

  473. <ul>
    474. 

  474. <li><strong>接続エラー</strong>: サーバーに到達できなかった場合。<code>res</code> が偽になり、<code>res.error()</code> でエラーの種類を取得できます</li>
    475. 

  475. <li><strong>HTTPエラー</strong>: サーバーからエラーステータス（404、500など）が返ってきた場合。<code>res</code> は真ですが、<code>res-&gt;status</code> を確認する必要があります</li>
    476. 

  476. </ul>
    477. 

  477. <h2>次のステップ</h2>
    478. 

  478. <p>クライアントからリクエストを送る方法がわかりました。次は、サーバー側をもっと詳しく見てみましょう。ルーティングやパスパラメータなど、サーバーの機能を掘り下げます。</p>
    479. 

  479. <p><strong>次:</strong> <a href="../03-basic-server">Basic Server</a></p>
    480. 

  480. 

  481.   </article>
    482. 

  482. </main>
    483. 

  483. 

  484.   </div>
    485. 

  485. 

  486.   <footer class="footer">
    487. 

  487.     &copy; 2026 yhirose. All rights reserved.
    488. 

  488.   </footer>
    489. 

  489. 

  490.   <script src="&#x2F;cpp-httplib/js/main.js"></script>
    491. 

  491. </body>
    492. 

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    493.