server_reference.cpp

//
// server.cpp
// ~~~~~~~~~~
//
// Copyright (c) 2003-2020 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 <boost/asio.hpp>
#include <boost/bind/bind.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <boost/shared_ptr.hpp>
#include <ctime>
#include <iostream>
#include <string>

using boost::asio::ip::tcp;

std::string make_daytime_string() {
    using namespace std; // For time_t, time and ctime;
    time_t now = time(0);
    return ctime(&now);
}

class tcp_connection : public boost::enable_shared_from_this<tcp_connection> {
   public:
    typedef boost::shared_ptr<tcp_connection> pointer;

    static pointer create(boost::asio::io_context& io_context) {
        return pointer(new tcp_connection(io_context));
    }

    tcp::socket& socket() { return socket_; }

    void start() {
        message_ = make_daytime_string();

        boost::asio::async_write(socket_, boost::asio::buffer(message_),
                                 boost::bind(&tcp_connection::handle_write, shared_from_this(),
                                             boost::asio::placeholders::error,
                                             boost::asio::placeholders::bytes_transferred));
    }

   private:
    tcp_connection(boost::asio::io_context& io_context) : socket_(io_context) {}

    void handle_write(const boost::system::error_code& /*error*/, size_t /*bytes_transferred*/) {}

    tcp::socket socket_;
    std::string message_;
};

class tcp_server {
   public:
    tcp_server(boost::asio::io_context& io_context)
        : io_context_(io_context)
        , acceptor_(io_context, tcp::endpoint(tcp::v4(), 13)) 
    {
        start_accept();
    }

   private:
    void start_accept() {
        tcp_connection::pointer new_connection 
            = tcp_connection::create(io_context_);

        acceptor_.async_accept(
            new_connection->socket(),
            boost::bind(
                &tcp_server::handle_accept, 
                this, 
                new_connection,
                boost::asio::placeholders::error));
    }

    void handle_accept(tcp_connection::pointer new_connection,
                       const boost::system::error_code& error) 
    {
        if (!error) {
            new_connection->start();
        }

        start_accept();
    }

    boost::asio::io_context& io_context_;
    tcp::acceptor acceptor_;
};

int main() {
    try {
        boost::asio::io_context io_context;
        tcp_server server(io_context);
        io_context.run();
    } catch (std::exception& e) {
        std::cerr << e.what() << std::endl;
    }

    return 0;
}