This tutorial program shows how to combine the two asynchronous servers that we have just written, into a single server application.

The main() function

int main()
{
  try
  {
    asio::io_context io_context;

We will begin by creating a server object to accept a TCP client connection.

    tcp_server server1(io_context);

We also need a server object to accept a UDP client request.

    udp_server server2(io_context);

We have created two lots of work for the io_context object to do.

    io_context.run();
  }
  catch (std::exception& e)
  {
    std::cerr << e.what() << std::endl;
  }

  return 0;
}

The tcp_connection and tcp_server classes

The following two classes are taken from Daytime.3.

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

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

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

  void start()
  {
    message_ = make_daytime_string();

    asio::async_write(socket_, asio::buffer(message_),
        std::bind(&tcp_connection::handle_write, shared_from_this()));
  }

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

  void handle_write()
  {
  }

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

class tcp_server
{
public:
  tcp_server(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(),
        std::bind(&tcp_server::handle_accept, this, new_connection,
          asio::placeholders::error));
  }

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

    start_accept();
  }

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

The udp_server class

Similarly, this next class is taken from the previous tutorial step.

class udp_server
{
public:
  udp_server(asio::io_context& io_context)
    : socket_(io_context, udp::endpoint(udp::v4(), 13))
  {
    start_receive();
  }

private:
  void start_receive()
  {
    socket_.async_receive_from(
        asio::buffer(recv_buffer_), remote_endpoint_,
        std::bind(&udp_server::handle_receive, this,
          asio::placeholders::error));
  }

  void handle_receive(const std::error_code& error)
  {
    if (!error)
    {
      std::shared_ptr<std::string> message(
          new std::string(make_daytime_string()));

      socket_.async_send_to(asio::buffer(*message), remote_endpoint_,
          std::bind(&udp_server::handle_send, this, message));

      start_receive();
    }
  }

  void handle_send(std::shared_ptr<std::string> /*message*/)
  {
  }

  udp::socket socket_;
  udp::endpoint remote_endpoint_;
  std::array<char, 1> recv_buffer_;
};

See the full source listing

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