Visual Studio Code python debugging timeout

I'm following Microsoft's guide Getting Started with Python in VS Code, but can only run in debug mode once -- the following run will always hit a time out issue.

This is the hello.py

msg = "Hello World"
print(msg)

This is the launch.json, which basically only added "stopOnEntry": true so will stop at the first line of code during debugging:

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [        
        {
            "name": "Python: Current File",
            "type": "python",
            "request": "launch",
            "program": "${file}",
            "console": "integratedTerminal",
            "stopOnEntry": true
        }
    ]
}

So my first round of debugging works, the terminal inside Visual Studio Code shows:

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\Playground\vscode\py\ms>c:/Playground/vscode/py/ms/env/Scripts/activate.bat
(env) C:\Playground\vscode\py\ms>cd c:\Playground\vscode\py\ms && cmd /C "set "PYTHONIOENCODING=UTF-8" && set "PYTHONUNBUFFERED=1" && c:\Playground\vscode\py\ms\env\Scripts\python.exe c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\ptvsd_launcher.py --default --client --host localhost --port 58792 c:\Playground\vscode\py\ms\hello.py "
Hello World

However, if I click debug button again, it jammed, showing an error dialogue:

[Window Title]
Visual Studio Code

[Content]
timeout

[Open launch.json] [Cancel]

, and Terminal inside vscode shows:

(env) C:\Playground\vscode\py\ms>cd c:\Playground\vscode\py\ms && cmd /C "set "PYTHONIOENCODING=UTF-8" && set "PYTHONUNBUFFERED=1" && c:\Playground\vscode\py\ms\env\Scripts\python.exe c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\ptvsd_launcher.py --default --client --host localhost --port 58798 c:\Playground\vscode\py\ms\hello.py "
E00001.107: Exception escaped from start_client

            Traceback (most recent call last):
              File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\log.py", line 110, in g
                return f(*args, **kwargs)
              File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\pydevd_hooks.py", line 74, in start_client
                sock, start_session = daemon.start_client((host, port))
              File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\daemon.py", line 217, in start_client
                connect(client, addr)
              File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\socket.py", line 197, in connect
                sock.connect(addr)
            ConnectionRefusedError: [WinError 10061] No connection could be made because the target machine actively refused it


Traceback (most recent call last):
  File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\ptvsd_launcher.py", line 43, in <module>
    main(ptvsdArgs)
  File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\__main__.py", line 434, in main
    run()
  File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\__main__.py", line 296, in run_file
    setup_connection()
  File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\__main__.py", line 287, in setup_connection
    daemon = ptvsd._remote.attach(addr)
  File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\_remote.py", line 91, in attach
    patch_multiprocessing=ptvsd.options.multiprocess)
  File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\_vendored\pydevd\pydevd.py", line 2017, in settrace
    wait_for_ready_to_run,
  File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\_vendored\pydevd\pydevd.py", line 2068, in _locked_settrace
    debugger.connect(host, port)  # Note: connect can raise error.
  File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\_vendored\pydevd\pydevd.py", line 914, in connect
    s = start_client(host, port)
  File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\pydevd_hooks.py", line 132, in <lambda>
    _start_client = (lambda h, p: start_client(daemon, h, p))
  File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\log.py", line 110, in g
    return f(*args, **kwargs)
  File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\pydevd_hooks.py", line 74, in start_client
    sock, start_session = daemon.start_client((host, port))
  File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\daemon.py", line 217, in start_client
    connect(client, addr)
  File "c:\Users\drlren\.vscode\extensions\ms-python.python-2019.5.18875\pythonFiles\lib\python\ptvsd\socket.py", line 197, in connect
    sock.connect(addr)
ConnectionRefusedError: [WinError 10061] No connection could be made because the target machine actively refused it

What happened? and how can I sort it out?