Using /@@migrate_to_volto on a docker-based Plone Classic, can't call block-conversion-tool running on localhost

Migrating a Plone Classic site using /@@migrate_to_volto typically requires that a block conversion utility be used.
The instructions here: Migrating from Plone Classic UI to Volto – Backend – Plone Upgrade Guide – Version-specific migration procedures and tips — Plone Documentation v6.0
provide a mechanism to run a block conversion utility on your local machine at http://localhost:5000/html

Unfortunately, my Plone site, running locally in docker, doesn't know how to reach that service, running on my local machine.

I'm sure there's an easier way, but what I did, was launch the block-conversion-tool on a remote server and then change the url to point there
e.g. (where is my remote machine)

Did you try adding blocks-conversion-tool to your compose file?

Actually no, but it sounds like a worthwhile approach.
I'm not sure that it would allow transparently pointing at http://localhost:5000/html?
I haven't tested this, but, my understanding is that localhost remains local to each machine, so I would still need to do a bit of fancy footwork to get access to it.
That said, it's certainly a simpler option.

Option A - a shared network

I could register a shared network in my compose file and point it at http://shared_net:5000/html or whatever.

Option B - modify the image to run blocks-conversion-tool in the same container

If you add the blocks_conversion_tool image as a service to your compose file (like 'convtool') and the services are in a shared docker network, your backend can find the service at name 'convtool'.

It's internal DNS magic provided by docker on the service name.

Thanks @fredvd... that's even simpler than declaring a "shared network"