I've incorprated the source code from https://github.com/istopwg/ippsample into an iOS app. Just out of curiosity I wanted to see if my iPad can print to an IPP Server service running on itself. The IPP server runs and I can successfully "print" to it from my mac (including when the IPP Server was running in the background). However, when I print from my iPad the IPP server doesn't show in the list of printers. Is there something in the architecture of an iOS device that stops this working?
I was able to print to the IPP Server on the iOS device from another iOS device.
I could find no answers online to this so asked Michael Sweet himself. His answer - "Local IPP services are explicitly filtered out from the iOS Print UI - we had some bad experiences with third-party applications trying to run in the background leading to the change, almost 7 years ago now..."