

Read-only, or the ability to edit filenames & upload files?
Read only: as per other answers here, basically any HTTP server. The easiest one I know would be darkhttpd, because it requires no config files and can be run without root.
Read write: I like WFM https://github.com/tenox7/wfm






As far as I understand, wireguard is designed so that it can’t be portscanned. Replies are never sent to packets unless they pass full auth.
This is both a blessing and a curse. It unfortunately means that if you misconfigure a key then your packets get silently ignored by the other party, no error messages or the likes, it’s as if the other party doesn’t exist.
EDIT: Yep, as per https://www.wireguard.com/protocol/