What causes http://localhost:8000 connection issues on some browsers?
Background
This morning I had an issue accessing a docker container exposing an apache webserver on port 8000. I expected to connect and show the website as (I thought) it had the previous evening but saw "This site cannot be reached" "connection refused" on Opera 69.0.3686.49.
Switching to Chrome and Edge(Chrome now!) the website worked and was accessible on .
Firefox had the same issue as Opera - although this seems to be trying to redirect to https:// which isn't configured on the apache webserver.
Investigations
I found both 127.0.0.1:8000 and localhost.:8000 worked with Opera, and 127.0.0.1:8000 http:\\localhost.:8000 worked on Firefox [http:// is necessary on some browsers to highlight it's a URL and not a search].
Clearly the website is up and running and there are no firewall issues, perhaps there is some DNS or caching issue which is preventing Opera and Firefox accessing the websites when using localhost:8000?
Question
Why?! I'd really like to know what's going on here and why the alternative IP based 127.0.0.1:8000 URL works consistently, why the localhost. change makes a difference and what the addition of the . notation accomplishes. It all seems a bit crazy.
