//
// server.cpp
// ~~~~~~~~~~
//
// Copyright (c) 2003-2016 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 <ctime>
#include <iostream>
#include <string>
#include <boost/asio.hpp>
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);
}
int main()
{
  try
  {
    boost::asio::io_service io_service;
    tcp::acceptor acceptor(io_service, tcp::endpoint(tcp::v4(), 13));
    for (;;)
    {
      tcp::socket socket(io_service);
      acceptor.accept(socket);
      std::string message = make_daytime_string();
      boost::system::error_code ignored_error;
      boost::asio::write(socket, boost::asio::buffer(message), ignored_error);
    }
  }
  catch (std::exception& e)
  {
    std::cerr << e.what() << std::endl;
  }
  return 0;
}

Возврат кDaytime.2 - синхронный TCP дневной сервер