ssl - Serving port 443 over http creates 400 Bad Request Error instead of redirect

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So for posterity sake, I am trying to
configure my server so that even when someone tries to go to go to http://
domain.com:443, they would be correctly redirected to the https version of the site
(https:// domain.com).

When testing something
like http:// domain.com:443, it does not redirect correctly to https:// domain.com, I
instead get hit with a 400 Bad Request page with the following
content:

Bad
Request

Your browser sent a request
that this server could not understand.
Reason: You're speaking plain HTTP to
an SSL-enabled server port.
Instead use the HTTPS scheme to access this URL,
please.

Apache/2.4.18 (Ubuntu) Server at
sub.domain.com Port
443

I tried
including the following lines in my 000-default.conf in the
*:80>:

RewriteEngine
            On 
RewriteCond %{HTTPS} off
RewriteRule (.*)
            https://%{SERVER_NAME}/$1
            [R,L]

But it didn't
work.

This issue occurs on all domains,
subdomains and the server IP itself.

Possibly
related, trying to do a dry run of letsencrypt returns the
following:

 Domain:
            domain.com
 Type: connection
 Detail: Failed to connect to
            123.123.123.123:443 for TLS-SNI-01

            challenge

For each and
every domain listed in the sites-enabled folder.

Answer

TL;TR: you cannot serve both HTTP and HTTPS on the same port
(443).

While it would be in theory
possible to figure out based on the first data from the client if the client is sending
a HTTP request (i.e. GET .. or similar) or is starting a TLS
handshake (\x16\x03...) most web servers don't do this. Instead
they expect the client to behave properly, that is use plain HTTP on one port (usually
80) and HTTPS on another port (usually 443).

Your URL of
http://example.com:443 is causing the browser to make a plain
HTTP request to port 443. But the server is expecting TLS there which means that your
plain HTTP request is unexpected. Apache is at least nice enough to check if the
incoming data for a plain HTTP request in this case so that it can offer you a more
useful description:

Reason: You're speaking plain HTTP to an SSL-enabled server port. Instead use
the HTTPS scheme to access this URL,
please.

If you try
such requests with other servers then they would either close the connection without any
error at all or just hang because they are still hoping to get a TLS handshake from the
client.