This tutorial program shows how to use asio to implement a server application with UDP.

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

Create an ip::udp::socket object to receive requests on UDP port 13.

    udp::socket socket(io_context, udp::endpoint(udp::v4(), 13));

Wait for a client to initiate contact with us. The remote_endpoint object will be populated by ip::udp::socket::receive_from().

    for (;;)
    {
      std::array<char, 1> recv_buf;
      udp::endpoint remote_endpoint;
      socket.receive_from(asio::buffer(recv_buf), remote_endpoint);

Determine what we are going to send back to the client.

      std::string message = make_daytime_string();

Send the response to the remote_endpoint.

      std::error_code ignored_error;
      socket.send_to(asio::buffer(message),
          remote_endpoint, 0, ignored_error);
    }
  }

Finally, handle any exceptions.

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

  return 0;
}

See the full source listing

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