slow http client based on boost::asio

I am using the following code, taken from boost tutorials, to get a json string from the server.

The problem is that it takes some time to execute, ie more than 2 seconds to finish and both client and server are on localhost. If I remove the last 2 lines of the program, ie this while:

while (boost::asio::read(socket, response, boost::asio::transfer_at_least(1), error))

the program executes extremely fast. What might the problem be?

        boost::asio::streambuf response;
        boost::asio::read_until(socket, response, "\r\n");

        std::istream response_stream(&response);
        std::string http_version;
        response_stream >> http_version;
        unsigned int status_code;
        response_stream >> status_code;
        std::string status_message;
        std::getline(response_stream, status_message);
        if (!response_stream || http_version.substr(0, 5) != "HTTP/")
        {
          std::cout << "Invalid response\n";
          return 1;
        }
        if (status_code != 200)
        {
          std::cout << "Response returned with status code " << status_code << "\n";
          return 1;
        }


        boost::asio::read_until(socket, response, "\r\n\r\n");

        // Process the response headers.
        std::string header;
        while (std::getline(response_stream, header) && header != "\r");


        if (response.size() > 0)
          std::cout << &response;

        // Read until EOF, writing data to output as we go.
        boost::system::error_code error;
        while (boost::asio::read(socket, response,
              boost::asio::transfer_at_least(1), error))
          std::cout << &response;
        if (error != boost::asio::error::eof)
          throw boost::system::system_error(error);

a tcpdump to show some data from the server

HTTP/1.1 200 OK
Connection: close
Content-Length: 42
Server: C/1.1
Date: Thu, 24 Nov 2016 07:47:27 GMT

{"Out":[1],"In":[1,2,3,4,5,6]}