asio: initial idf port of asio library without ssl

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

examples/protocols/asio/chat_client/main/Kconfig.projbuild

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+menu "Example Configuration"
+
+config ESP_WIFI_SSID
+    string "WiFi SSID"
+    default "myssid"
+    help
+	SSID (network name) for the example to connect to.
+
+config ESP_WIFI_PASSWORD
+    string "WiFi Password"
+    default "mypassword"
+    help
+	WiFi password (WPA or WPA2) for the example to use.
+
+config EXAMPLE_PORT
+    string "asio example port number"
+    default "2222"
+    help
+    Port number used by ASIO example
+
+config EXAMPLE_SERVER_IP
+    string "asio example server ip for this client to connect to (leave defalut=FROM_STDIN to enter the server address via serial terminal)"
+    default "FROM_STDIN"
+    help
+    Please set the host name or ip address of corespondant server running
+
+endmenu

examples/protocols/asio/chat_client/main/chat_client.cpp

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+//
+// chat_client.cpp
+// ~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2018 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#include <cstdlib>
+#include <deque>
+#include <iostream>
+#include <thread>
+#include "asio.hpp"
+#include "chat_message.hpp"
+
+using asio::ip::tcp;
+
+typedef std::deque<chat_message> chat_message_queue;
+
+class chat_client
+{
+public:
+  chat_client(asio::io_context& io_context,
+      const tcp::resolver::results_type& endpoints)
+    : io_context_(io_context),
+      socket_(io_context)
+  {
+    do_connect(endpoints);
+  }
+
+  void write(const chat_message& msg)
+  {
+    asio::post(io_context_,
+        [this, msg]()
+        {
+          bool write_in_progress = !write_msgs_.empty();
+          write_msgs_.push_back(msg);
+          if (!write_in_progress)
+          {
+            do_write();
+          }
+        });
+  }
+
+  void close()
+  {
+    asio::post(io_context_, [this]() { socket_.close(); });
+  }
+
+private:
+  void do_connect(const tcp::resolver::results_type& endpoints)
+  {
+    asio::async_connect(socket_, endpoints,
+        [this](std::error_code ec, tcp::endpoint)
+        {
+          if (!ec)
+          {
+            do_read_header();
+          }
+        });
+  }
+
+  void do_read_header()
+  {
+    asio::async_read(socket_,
+        asio::buffer(read_msg_.data(), chat_message::header_length),
+        [this](std::error_code ec, std::size_t /*length*/)
+        {
+          if (!ec && read_msg_.decode_header())
+          {
+            do_read_body();
+          }
+          else
+          {
+            socket_.close();
+          }
+        });
+  }
+
+  void do_read_body()
+  {
+    asio::async_read(socket_,
+        asio::buffer(read_msg_.body(), read_msg_.body_length()),
+        [this](std::error_code ec, std::size_t /*length*/)
+        {
+          if (!ec)
+          {
+            std::cout.write(read_msg_.body(), read_msg_.body_length());
+            std::cout << "\n";
+            do_read_header();
+          }
+          else
+          {
+            socket_.close();
+          }
+        });
+  }
+
+  void do_write()
+  {
+    asio::async_write(socket_,
+        asio::buffer(write_msgs_.front().data(),
+          write_msgs_.front().length()),
+        [this](std::error_code ec, std::size_t /*length*/)
+        {
+          if (!ec)
+          {
+            write_msgs_.pop_front();
+            if (!write_msgs_.empty())
+            {
+              do_write();
+            }
+          }
+          else
+          {
+            socket_.close();
+          }
+        });
+  }
+
+private:
+  asio::io_context& io_context_;
+  tcp::socket socket_;
+  chat_message read_msg_;
+  chat_message_queue write_msgs_;
+};
+
+void read_line(char * line, int max_chars);
+
+
+void asio_main()
+{
+    std::string name(CONFIG_EXAMPLE_SERVER_IP);
+    std::string port(CONFIG_EXAMPLE_PORT);
+    char line[chat_message::max_body_length + 1] = { 0 };
+
+    if (name == "FROM_STDIN") {
+      std::cout << "Please enter ip address of chat server" << std::endl;
+      if (std::cin.getline(line, chat_message::max_body_length + 1)) {
+        name = line;
+        std::cout << "Chat server IP:" << name << std::endl;
+      }
+    }
+
+    asio::io_context io_context;
+    tcp::resolver resolver(io_context);
+    auto endpoints = resolver.resolve(name, port);
+
+    chat_client c(io_context, endpoints);
+
+    std::thread t([&io_context](){ io_context.run(); });
+
+    while (std::cin.getline(line, chat_message::max_body_length + 1) && std::string(line) != "exit\n") {
+      chat_message msg;
+      msg.body_length(std::strlen(line));
+      std::memcpy(msg.body(), line, msg.body_length());
+      msg.encode_header();
+      c.write(msg);
+    }
+
+    c.close();
+    t.join();
+}

examples/protocols/asio/chat_client/main/chat_message.hpp

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+//
+// chat_message.hpp
+// ~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2018 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#ifndef CHAT_MESSAGE_HPP
+#define CHAT_MESSAGE_HPP
+
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+
+class chat_message
+{
+public:
+  enum { header_length = 4 };
+  enum { max_body_length = 512 };
+
+  chat_message()
+    : body_length_(0)
+  {
+  }
+
+  const char* data() const
+  {
+    return data_;
+  }
+
+  char* data()
+  {
+    return data_;
+  }
+
+  std::size_t length() const
+  {
+    return header_length + body_length_;
+  }
+
+  const char* body() const
+  {
+    return data_ + header_length;
+  }
+
+  char* body()
+  {
+    return data_ + header_length;
+  }
+
+  std::size_t body_length() const
+  {
+    return body_length_;
+  }
+
+  void body_length(std::size_t new_length)
+  {
+    body_length_ = new_length;
+    if (body_length_ > max_body_length)
+      body_length_ = max_body_length;
+  }
+
+  bool decode_header()
+  {
+    char header[header_length + 1] = "";
+    std::strncat(header, data_, header_length);
+    body_length_ = std::atoi(header);
+    if (body_length_ > max_body_length)
+    {
+      body_length_ = 0;
+      return false;
+    }
+    return true;
+  }
+
+  void encode_header()
+  {
+    char header[header_length + 1] = "";
+    std::sprintf(header, "%4d", static_cast<int>(body_length_));
+    std::memcpy(data_, header, header_length);
+  }
+
+private:
+  char data_[header_length + max_body_length];
+  std::size_t body_length_;
+};
+
+#endif // CHAT_MESSAGE_HPP

examples/protocols/asio/chat_client/main/component.mk

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+#
+# Main component makefile.
+#
+# This Makefile can be left empty. By default, it will take the sources in the 
+# src/ directory, compile them and link them into lib(subdirectory_name).a 
+# in the build directory. This behaviour is entirely configurable,
+# please read the ESP-IDF documents if you need to do this.
+#