text: //
  // stream_server.cpp
  // ~~~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2017 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 <array>
  #include <cstdio>
  #include <iostream>
  #include <memory>
  #include "asio.hpp"
  
  #if defined(ASIO_HAS_LOCAL_SOCKETS)
  
  using asio::local::stream_protocol;
  
  class session
    : public std::enable_shared_from_this<session>
  {
  public:
    session(stream_protocol::socket sock)
      : socket_(std::move(sock))
    {
    }
  
    void start()
    {
      do_read();
    }
  
  private:
    void do_read()
    {
      auto self(shared_from_this());
      socket_.async_read_some(asio::buffer(data_),
          [this, self](std::error_code ec, std::size_t length)
          {
            if (!ec)
              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();
          });
    }
  
    // The socket used to communicate with the client.
    stream_protocol::socket socket_;
  
    // Buffer used to store data received from the client.
    std::array<char, 1024> data_;
  };
  
  class server
  {
  public:
    server(asio::io_context& io_context, const std::string& file)
      : acceptor_(io_context, stream_protocol::endpoint(file))
    {
      do_accept();
    }
  
  private:
    void do_accept()
    {
      acceptor_.async_accept(
          [this](std::error_code ec, stream_protocol::socket socket)
          {
            if (!ec)
            {
              std::make_shared<session>(std::move(socket))->start();
            }
  
            do_accept();
          });
    }
  
    stream_protocol::acceptor acceptor_;
  };
  
  int main(int argc, char* argv[])
  {
    try
    {
      if (argc != 2)
      {
        std::cerr << "Usage: stream_server <file>\n";
        std::cerr << "*** WARNING: existing file is removed ***\n";
        return 1;
      }
  
      asio::io_context io_context;
  
      std::remove(argv[1]);
      server s(io_context, argv[1]);
  
      io_context.run();
    }
    catch (std::exception& e)
    {
      std::cerr << "Exception: " << e.what() << "\n";
    }
  
    return 0;
  }
  
  #else // defined(ASIO_HAS_LOCAL_SOCKETS)
  # error Local sockets not available on this platform.
  #endif // defined(ASIO_HAS_LOCAL_SOCKETS)
  