Problem

When we try to use a restricted port between 1-1023 we get a panic and the browser is still opened and reports a missing service.

mdbook serve test_book --open --port 83

I tried a few ports.

The same if we already have a book served on some good port (e.g. the default 3000) and we start a new book one the same port.
mdbook panics and opens the browser on that port, but that shows the other book.

Steps

For the first one just run

mdbook serve test_book --open --port 83

For the second problem in one window run

mdbook serve test_book

And then in another window run

mdbook serve test_book --open

Possible Solution(s)

No response

Notes

No response

Version

Both `mdbook v0.4.47` and what we have in `master`.