Asynchronous TCP server not reading message from boost::asio socket?

Question

C++ / C#

Here is my asynchronous TCP server code, I write it like the example code from the boost site

#include <iostream>
#include <boost/bind.hpp>
#include <boost/asio.hpp>

using namespace boost::asio;
using namespace std;

class session
{
public:
  session(io_service& service) : socket(service)
  {
  }

  ip::tcp::socket& get_socket()
  {
    return socket;
  }

  void start()
  {
    socket.async_read_some(
      boost::asio::buffer(buff, message_lenght),
      boost::bind(
        &session::read_handler,
        this,
        boost::asio::placeholders::error,
        boost::asio::placeholders::bytes_transferred
      )
    );
  }

private:
  ip::tcp::socket socket;
  enum { message_lenght = 1024 };
  char buff[message_lenght] = { };

  void read_handler(
    const boost::system::error_code& error,
    std::size_t bytes_transferred
  )
  {
    if (!error)
    {
      async_write(
        socket,
        boost::asio::buffer(buff, message_lenght),
        boost::bind(
          &session::write_handler,
          this,
          boost::asio::placeholders::error,
          boost::asio::placeholders::bytes_transferred
        )
      );
    }
    {
      cout << "read error " << error.message() << endl;
      delete this;
    }
  }

  void write_handler(
    const boost::system::error_code& error,
    std::size_t bytes_transferred
  )
  {
    if (!error)
    {
      socket.async_read_some(
        boost::asio::buffer(buff, message_lenght),
        boost::bind(
          &session::read_handler,
          this,
          boost::asio::placeholders::error,
          boost::asio::placeholders::bytes_transferred
        )
      );
    }
    else
    {
      cout << "read error " << error.message() << endl;
      delete this;
    }
  }
};

class server
{
public:
  server(boost::asio::io_service& service, short port) : service_(),
    acceptor(service, ip::tcp::endpoint(ip::tcp::v4(), port))
  {
    start_accept();
  }
private:
  short port;
  io_service service_;
  ip::tcp::acceptor acceptor;
  
  void start_accept()
  {
    session* new_session = new session(service_);
    acceptor.async_accept(
      new_session->get_socket(),
      boost::bind(
        &server::handle_accept,
        this,
        new_session,
        boost::asio::placeholders::error
      )
    );
  }

  void handle_accept(
    session* new_session,
    const boost::system::error_code& error
  )
  {
    if (!error)
    {
      new_session->start();
    }
    else
    {
      cout << "accept error " << error.message() << endl;
      delete new_session;
    }
    start_accept();
  }
};

int main()
{
  setlocale(LC_ALL, "Rus");
  io_service service;
  server* s = new server(service, 5000);
  service.run();
}

It accepts the connection but does not read the message from the client.