I decided to try it in my linux box and see if it would work. It did.
It makes me think that there is a step or configuration that might be missing for the Mocha installation. Was there any kind of tutorial over device/printer setup or anything like that? Did your instructor give directions about the program and software setup?
It works, apparently, for the same AS400 server on my linux distro. It just seems to have the same problem as you do with the Windows port, but the function works fine in a different terminal client.