### Daytime.7 - A combined TCP/UDP asynchronous server

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_;
    };

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