add: exercise answer for chapter 6 and 7

exercises/6/server.http.hpp

@@ -0,0 +1,38 @@
+//
+// server_http.hpp
+// web_server
+// created by changkun at changkun.de/modern-cpp
+//
+
+#ifndef SERVER_HTTP_HPP
+#define	SERVER_HTTP_HPP
+
+#include "server.base.hpp"
+
+namespace LabexWeb {
+    typedef boost::asio::ip::tcp::socket HTTP;
+    template<>
+    class Server<HTTP> : public ServerBase<HTTP> {
+    public:
+        // use port, thread number to construct web server
+        // http server is much simple than https since it doesn't need to initial config file
+        Server(unsigned short port, size_t num_threads=1) :
+            ServerBase<HTTP>::ServerBase(port, num_threads) {};
+    private:
+        // implement accept() method
+        void accept() {
+            // create a new socket for current connection
+            // shared_ptr is used for passing temporal object to anonymous function
+            // socket will be deduce as type of std::shared_ptr<HTTP>
+            auto socket = std::make_shared<HTTP>(m_io_service);
+
+            acceptor.async_accept(*socket, [this, socket](const boost::system::error_code& ec) {
+                // establish a connection
+                accept();
+                // if no error
+                if(!ec) process_request_and_respond(socket);
+            });
+        }
+    };
+}
+#endif	/* SERVER_HTTP_HPP */