Asio and HTTP keep-alive

I am trying to implement a web server using asio, but although the acceptor is not supported, when I receive a connection, after sending a response, the socket always closes, read from the socket (to implement keep-alive with http).

I tried to insert printfs into the code, and for some reason, after I write the answer, when the client creates a new connection, it calls the acceptor on my socket, shouldn't it just use the old socket and re-read from it instead of calling the acceptor?

Or am I using the keep-alive function in the wrong way ...

Relevant piece of code:

#include "connection.hpp"
#include <vector>
#include <boost/bind.hpp>
#include "connection_manager.hpp"
#include "request_handler.hpp"
#include <iostream>

namespace http {
namespace server {

connection::connection(asio::io_service& io_service,
    connection_manager& manager, request_handler& handler)
  : socket_(io_service),
    connection_manager_(manager),
    request_handler_(handler),
    request_parser_(new http_visitor()),
    keep_alive_(true)
{
}

asio::ip::tcp::socket& connection::socket()
{
  return socket_;
}

void connection::start()
{
  socket_.async_read_some(asio::buffer(buffer_),
      boost::bind(&connection::handle_read, shared_from_this(),
        asio::placeholders::error,
        asio::placeholders::bytes_transferred));
  std::cout << "In connection start" << std::endl;
}

void connection::stop()
{
  socket_.close();
}

void connection::handle_read(const asio::error_code& e,
    std::size_t bytes_transferred)
{
  if (!e)
  {
    boost::tribool result;
    boost::tie(result, boost::tuples::ignore) = request_parser_.parse(
        request_, buffer_.data(), buffer_.data() + bytes_transferred);

    if (result)
    {
      request_handler_.handle_request(request_, reply_);

      std::vector<header>::iterator hdr_it;

      for(hdr_it = request_.headers.begin(); hdr_it != request_.headers.end();     hdr_it++)
      {
            if( (hdr_it->name.compare("Connection" ) == 0) && 
                (hdr_it->value.compare("close" ) == 0 ) )
        { keep_alive_ = false; }   
      }

      asio::async_write(socket_, reply_.to_buffers(),
                    boost::bind(&connection::handle_write, shared_from_this(),
                    asio::placeholders::error));
    }
    else if (!result)
    {
      reply_ = reply::stock_reply(reply::bad_request);
      asio::async_write(socket_, reply_.to_buffers(),
          boost::bind(&connection::handle_write, shared_from_this(),
            asio::placeholders::error));
    }
    else
    {
      socket_.async_read_some(asio::buffer(buffer_),
          boost::bind(&connection::handle_read, shared_from_this(),
            asio::placeholders::error,
            asio::placeholders::bytes_transferred));
    }
  }
  else if (e != asio::error::operation_aborted)
  {
    connection_manager_.stop(shared_from_this());
  }
}

void connection::handle_write(const asio::error_code& e)
{
  if (!e)
  {

    std::cout << keep_alive_ << std::endl;
    if(keep_alive_)
    {
      buffer_.assign(0);
      request_.clear();
      keep_alive_ = false;
      start();
    }
    else
    {
      socket_.close();
    }  
  }

  if (e != asio::error::operation_aborted)
  {
    connection_manager_.stop(shared_from_this());
  }
}
}
}

and

#include "server.hpp"
#include <boost/bind.hpp>
#include <signal.h>
#include <iostream>

namespace http {
namespace server {

server::server(const std::string& address, const std::string& port,
    const std::string& doc_root)
  : io_service_(),
    signals_(io_service_),
    acceptor_(io_service_),
    connection_manager_(),
    new_connection_(new connection(io_service_, connection_manager_, request_handler_)),
    request_handler_(doc_root)
{
  signals_.add(SIGINT);
  signals_.add(SIGTERM);
  signals_.async_wait(boost::bind(&server::handle_stop, this));

  // Open the acceptor with the option to reuse the address (i.e. SO_REUSEADDR).
  asio::ip::tcp::resolver resolver(io_service_);
  asio::ip::tcp::resolver::query query(address, port);
  asio::ip::tcp::endpoint endpoint = *resolver.resolve(query);
  acceptor_.open(endpoint.protocol());
  acceptor_.set_option(asio::ip::tcp::acceptor::reuse_address(true));
  acceptor_.set_option(asio::ip::tcp::acceptor::keep_alive(true));
  acceptor_.bind(endpoint);
  acceptor_.listen();
  acceptor_.async_accept(new_connection_->socket(),
      boost::bind(&server::handle_accept, this,
        asio::placeholders::error));
}

void server::run()
{
    io_service_.run();
}

void server::stop()
{
  io_service_.post(boost::bind(&server::handle_stop, this));
}

void server::handle_accept(const asio::error_code& e)
{
  if (!e)
  {
   std::cout << "In accept" << std::endl;
    connection_manager_.start(new_connection_);
    new_connection_.reset(new connection(io_service_, connection_manager_,     request_handler_));
    acceptor_.async_accept(new_connection_->socket(),
        boost::bind(&server::handle_accept, this, asio::placeholders::error));
  }
}

void server::handle_stop()
{
  acceptor_.close();
  connection_manager_.stop_all();
}

} // namespace server
} // namespace http

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