asio: initial idf port of asio library without ssl

* Original commit: espressif/esp-idf@1ef13c524c

examples/protocols/asio/tcp_echo_server/main/echo_server.cpp

@@ -0,0 +1,91 @@
+#include "asio.hpp"
+#include <string>
+#include <iostream>
+
+using asio::ip::tcp;
+
+class session
+  : public std::enable_shared_from_this<session>
+{
+public:
+  session(tcp::socket socket)
+    : socket_(std::move(socket))
+  {
+  }
+
+  void start()
+  {
+    do_read();
+  }
+
+private:
+  void do_read()
+  {
+    auto self(shared_from_this());
+    socket_.async_read_some(asio::buffer(data_, max_length),
+        [this, self](std::error_code ec, std::size_t length)
+        {
+          if (!ec)
+          {
+            std::cout << data_ << std::endl;
+            do_write(length);
+          }
+        });
+  }
+
+  void do_write(std::size_t length)
+  {
+    auto self(shared_from_this());
+    asio::async_write(socket_, asio::buffer(data_, length),
+        [this, self](std::error_code ec, std::size_t length)
+        {
+          if (!ec)
+          {
+            do_read();
+          }
+        });
+  }
+
+  tcp::socket socket_;
+  enum { max_length = 1024 };
+  char data_[max_length];
+};
+
+class server
+{
+public:
+  server(asio::io_context& io_context, short port)
+    : acceptor_(io_context, tcp::endpoint(tcp::v4(), port))
+  {
+    do_accept();
+  }
+
+private:
+  void do_accept()
+  {
+    acceptor_.async_accept(
+        [this](std::error_code ec, tcp::socket socket)
+        {
+          if (!ec)
+          {
+            std::make_shared<session>(std::move(socket))->start();
+          }
+
+          do_accept();
+        });
+  }
+
+  tcp::acceptor acceptor_;
+};
+
+
+void asio_main()
+{
+
+    asio::io_context io_context;
+
+    server s(io_context, std::atoi(CONFIG_EXAMPLE_PORT));
+
+    io_context.run();
+
+}