Function get_daytime

example/cpp11/futures/daytime_client.cpp:21–65

using boost::asio::ip::udp;

void get_daytime(boost::asio::io_context& io_context, const char* hostname)
{
  try
  {
    udp::resolver resolver(io_context);

    std::future<udp::resolver::results_type> endpoints =
      resolver.async_resolve(
          udp::v4(), hostname, "daytime",
          boost::asio::use_future);

    // The async_resolve operation above returns the endpoints as a future
    // value that is not retrieved ...

    udp::socket socket(io_context, udp::v4());

    std::array<char, 1> send_buf  = {{ 0 }};
    std::future<std::size_t> send_length =
      socket.async_send_to(boost::asio::buffer(send_buf),
          *endpoints.get().begin(), // ... until here. This call may block.
          boost::asio::use_future);

    // Do other things here while the send completes.

    send_length.get(); // Blocks until the send is complete. Throws any errors.

    std::array<char, 128> recv_buf;
    udp::endpoint sender_endpoint;
    std::future<std::size_t> recv_length =
      socket.async_receive_from(
          boost::asio::buffer(recv_buf),
          sender_endpoint,
          boost::asio::use_future);

    // Do other things here while the receive completes.

    std::cout.write(
        recv_buf.data(),
        recv_length.get()); // Blocks until receive is complete.
  }
  catch (boost::system::system_error& e)
  {
    std::cerr << e.what() << std::endl;
  }
}

int main(int argc, char* argv[])
{