Can't seem to find a corresponding wraperServerTLS to the client function Tim posted.
There is no wrapServerTLS right now in Twisted itself.
https://github.com/glyph/txsni/blob/master/txsni/tlsendpoint.py is available in txsni though; arguably all of txsni should be in Twisted, but certainly this should be. If you wanted to write a PR that added some docstrings and unit tests that would be great :).