How can I debug one browser with VNC using selenium grid?

I want to have a selenium grid using example provided in the repository:

# To execute this docker-compose yml file use `docker-compose -f docker-compose-v3-full-grid.yml up`
# Add the `-d` flag at the end for detached execution
# To stop the execution, hit Ctrl+C, and then `docker-compose -f docker-compose-v3-full-grid.yml down`
version: "3"
services:
  selenium-event-bus:
    image: selenium/event-bus:4.1.1-20211217
    container_name: selenium-event-bus
    ports:
      - "4442:4442"
      - "4443:4443"
      - "5557:5557"

  selenium-sessions:
    image: selenium/sessions:4.1.1-20211217
    container_name: selenium-sessions
    ports:
      - "5556:5556"
    depends_on:
      - selenium-event-bus
    environment:
      - SE_EVENT_BUS_HOST=selenium-event-bus
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443

  selenium-session-queue:
    image: selenium/session-queue:4.1.1-20211217
    container_name: selenium-session-queue
    ports:
      - "5559:5559"
    depends_on:
      - selenium-event-bus
    environment:
      - SE_EVENT_BUS_HOST=selenium-event-bus
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443

  selenium-distributor:
    image: selenium/distributor:4.1.1-20211217
    container_name: selenium-distributor
    ports:
      - "5553:5553"
    depends_on:
      - selenium-event-bus
      - selenium-sessions
      - selenium-session-queue
    environment:
      - SE_EVENT_BUS_HOST=selenium-event-bus
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443
      - SE_SESSIONS_MAP_HOST=selenium-sessions
      - SE_SESSIONS_MAP_PORT=5556
      - SE_SESSION_QUEUE_HOST=selenium-session-queue
      - SE_SESSION_QUEUE_PORT=5559

  selenium-router:
    image: selenium/router:4.1.1-20211217
    container_name: selenium-router
    ports:
      - "4444:4444"
    depends_on:
      - selenium-distributor
      - selenium-sessions
      - selenium-session-queue
    environment:
      - SE_DISTRIBUTOR_HOST=selenium-distributor
      - SE_DISTRIBUTOR_PORT=5553
      - SE_SESSIONS_MAP_HOST=selenium-sessions
      - SE_SESSIONS_MAP_PORT=5556
      - SE_SESSION_QUEUE_HOST=selenium-session-queue
      - SE_SESSION_QUEUE_PORT=5559

  chrome:
    image: selenium/node-chrome:4.1.1-20211217
    shm_size: 2gb
    depends_on:
      - selenium-event-bus
    environment:
      - SE_EVENT_BUS_HOST=selenium-event-bus
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443

  edge:
    image: selenium/node-edge:4.1.1-20211217
    shm_size: 2gb
    depends_on:
      - selenium-event-bus
    environment:
      - SE_EVENT_BUS_HOST=selenium-event-bus
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443

  firefox:
    image: selenium/node-firefox:4.1.1-20211217
    shm_size: 2gb
    depends_on:
      - selenium-event-bus
    environment:
      - SE_EVENT_BUS_HOST=selenium-event-bus
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443

This opens the selenium grid with the view of the different nodes on http://127.0.0.1:4444/ui/index.html#/:

Now I want to execute a test using a code I'm not sure where I copied it, but is not mine:

import os
import datetime
import time
import unittest
from selenium import webdriver
 
 
class Example(unittest.TestCase):
 
    def setUp(self):
 
        self.driver = webdriver.Remote(
            command_executor='http://127.0.0.1:4444/wd/hub',
            desired_capabilities={
                'browserName': 'firefox',
                'javascriptEnabled': True
            }
        )
 
        self.driver.get('https://google.es/')
 
    def test_something(self):
 
        dt_format = '%Y%m%d_%H%M%S'
        cdt = datetime.datetime.fromtimestamp(time.time()).strftime(dt_format)
        current_location = os.getcwd()
        img_folder = current_location + '/images/'
 
        if not os.path.exists(img_folder):
            os.mkdir(img_folder)
 
        picture = img_folder + cdt + '.png'
        self.driver.save_screenshot(picture)
        print('Waiting 160sec...')
        time.sleep(160)
        print('Done waiting...')
 
    def tearDown(self):
 
        self.driver.quit()
 
 
if __name__ == "__main__":
 
    unittest.main(verbosity=1)

The code works as expected as a screenshot of the google page is saved. But I'd like to check the browser in this waiting time, so I added to chrome the ports:

ports:
 - 5900:5900 

And I'm able to open a VNC connection with VNC Viewer with the OS of the node, but I'm not able to see the browser that is running my test.

The url from the selenium grid to each node is also not working

How can I access the specific browser of my test?

The test says

desired_capabilities={
    'browserName': 'firefox',
    'javascriptEnabled': True
}

while you mentioned you "added to chrome the ports", so I suspect you were looking at the wrong node.

I recommend you open all the VNC ports for all nodes, as described here.
I also recommend noVNC.