void send_message (std::string message){
    send (server_fd, message.c_str(), strlen (message.c_str()), 0);
  }

  std::string receive_message (){
    Buffer b;
    int nbytes = recv (server_fd, b.pointer, b.capacity(), 0);

    if (nbytes == -1){
      std::cout << "erro ao receber mensagem\n";
    }
    return b.to_string();
  }