def shift_string(buffer)
      len = shift_short(buffer)
      str = shift_data(buffer, len)
      # Strings in MQTT v3.1 are all UTF-8
      str.force_encoding('UTF-8')
    end
def shift_string(buffer)
      len = shift_short(buffer)
      str = shift_data(buffer, len)
      # Strings in MQTT v3.1 are all UTF-8
      str.force_encoding('UTF-8')
    end
Remove string from the front of buffer