Is Google able to crawl protocols other than http and https?

Matt's answer:
Today’s question comes from Daniel or Daniel– I’m really bad with umlauts, I apologize– Voogsgerd from the Netherlands. The question is, Is Google able to crawl more protocols than http and https? I believe the answer is yes. I believe we have support to crawl FTP. But really that’s pretty far off the beaten path. So, if at all possible, I would try to make sure that your pages are http or https. We did build a crawler way back in the day with the support for multiple protocols. So the ability to crawl everything from WML and WAP and stuff like that, if you’ve known about those types of mark up language. But in general it’s usually best if you stick to the well-beaten path of http or https.
by Matt Cutts - Google's Head of Search Quality Team