Looking for the name(s) of companies who provide boat service from Sorrento to Naples and to Positano in mid-October, 2017.
This is a good website to reference although schedules for 2017 aren't up yet. You can get an approximation of what times they were running last fall, though.
I think we used these ferry companies on that area: Aliscafi and Caremar
The capribooking website lists the names of the companies providing service for each listing on the schedule along with type of craft.