안녕하십니까 덕분에 자연어처리 공부에 큰 도움을 받고 있습니다.
다름이 아니라 공부중 4장 5단계 웹서비스 시작하기 단계에서 자꾸 오류가 발생하여 질문 드리게 되었습니다.
인증 토큰을 입력후, 5단계 코드 4-26을 실행하였으나, 아래와 같은 오류가 자꾸 발생합니다. 혹시 해결책을 알 수 있을까 해서 글 남깁니다. 감사합니다. 따뜻한 봄날 보내세요^^

• Serving Flask app 'ratsnlp.nlpbook.classification.deploy'
• Debug mode: off
  INFO:werkzeug:WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
• Running on http://127.0.0.1:5000/
  INFO:werkzeug:Press CTRL+C to quit
  Exception in thread Thread-13:
  Traceback (most recent call last):
  File "/usr/local/lib/python3.10/dist-packages/urllib3/connection.py", line 203, in _new_conn
  sock = connection.create_connection(
  File "/usr/local/lib/python3.10/dist-packages/urllib3/util/connection.py", line 85, in create_connection
  raise err
  File "/usr/local/lib/python3.10/dist-packages/urllib3/util/connection.py", line 73, in create_connection
  sock.connect(sa)
  ConnectionRefusedError: [Errno 111] Connection refused

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/usr/local/lib/python3.10/dist-packages/urllib3/connectionpool.py", line 791, in urlopen
response = self._make_request(
File "/usr/local/lib/python3.10/dist-packages/urllib3/connectionpool.py", line 497, in _make_request
conn.request(
File "/usr/local/lib/python3.10/dist-packages/urllib3/connection.py", line 395, in request
self.endheaders()
File "/usr/lib/python3.10/http/client.py", line 1278, in endheaders
self._send_output(message_body, encode_chunked=encode_chunked)
File "/usr/lib/python3.10/http/client.py", line 1038, in _send_output
self.send(msg)
File "/usr/lib/python3.10/http/client.py", line 976, in send
self.connect()
File "/usr/local/lib/python3.10/dist-packages/urllib3/connection.py", line 243, in connect
self.sock = self._new_conn()
File "/usr/local/lib/python3.10/dist-packages/urllib3/connection.py", line 218, in _new_conn
raise NewConnectionError(
urllib3.exceptions.NewConnectionError: <urllib3.connection.HTTPConnection object at 0x7dbbb78b8640>: Failed to establish a new connection: [Errno 111] Connection refused

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/usr/local/lib/python3.10/dist-packages/requests/adapters.py", line 486, in send
resp = conn.urlopen(
File "/usr/local/lib/python3.10/dist-packages/urllib3/connectionpool.py", line 845, in urlopen
retries = retries.increment(
File "/usr/local/lib/python3.10/dist-packages/urllib3/util/retry.py", line 515, in increment
raise MaxRetryError(_pool, url, reason) from reason # type: ignore[arg-type]
urllib3.exceptions.MaxRetryError: HTTPConnectionPool(host='localhost', port=4040): Max retries exceeded with url: /api/tunnels (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7dbbb78b8640>: Failed to establish a new connection: [Errno 111] Connection refused'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/usr/lib/python3.10/threading.py", line 1016, in _bootstrap_inner
self.run()
File "/usr/lib/python3.10/threading.py", line 1378, in run
self.function(*self.args, **self.kwargs)
File "/usr/local/lib/python3.10/dist-packages/flask_ngrok.py", line 70, in start_ngrok
ngrok_address = _run_ngrok()
File "/usr/local/lib/python3.10/dist-packages/flask_ngrok.py", line 35, in _run_ngrok
tunnel_url = requests.get(localhost_url).text # Get the tunnel information
File "/usr/local/lib/python3.10/dist-packages/requests/api.py", line 73, in get
return request("get", url, params=params, **kwargs)
File "/usr/local/lib/python3.10/dist-packages/requests/api.py", line 59, in request
return session.request(method=method, url=url, **kwargs)
File "/usr/local/lib/python3.10/dist-packages/requests/sessions.py", line 589, in request
resp = self.send(prep, **send_kwargs)
File "/usr/local/lib/python3.10/dist-packages/requests/sessions.py", line 703, in send
r = adapter.send(request, **kwargs)
File "/usr/local/lib/python3.10/dist-packages/requests/adapters.py", line 519, in send
raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPConnectionPool(host='localhost', port=4040): Max retries exceeded with url: /api/tunnels (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7dbbb78b8640>: Failed to establish a new connection: [Errno 111] Connection refused'))