It supports its own custom binary protocol and the MySQL protocol (recently they also added a HTTP API). When you see "listen = localhost:9306:mysql41" in the config, that means it's listening for MySQL protocol traffic on port 9306.
https://github.com/a1tus/sphinxapi-py3 appears to be the best Python client for the binary api at the moment. This doesn't support INSERTing things into the index (you'll need to use the MySQL protocol for that).
It does not match partial words by default. Turning on partial matching can also increase the size of your index dramatically. You can also limit the fields that support partial matching with the "infix_fields" and "prefix_fields" setting.
Stemmers aren't turned on by default. So, searching for "dog" will not match "dogs".
Most special characters ($, @, &, etc) are ignored by default. You will need to add them to charset_table if you want them to be searchable.
I had a unique constraint on a VARCHAR column and I inserted two rows with the following values:
"name" (without trailing whitespace)
"name " (with trailing whitespace)
To my surprise, I got a duplicate error on that 2nd insert. It turns out that MySQL ignores that trailing whitespace when it makes comparisons.
The MySQL docs say this: "All MySQL collations are of type PAD SPACE. This means that all CHAR, VARCHAR, and TEXT values are compared without regard to any trailing spaces. “Comparison” in this context does not include the LIKE pattern-matching operator, for which trailing spaces are significant." (https://dev.mysql.com/doc/refman/5.7/en/char.html)
The solution? You should probably be trimming trailing whitespace in your API endpoints and on your front-end.