Did your RS-232 cable fail? That would be my first check.
I have yet to use an RJ-45 connection. I think the idea is this allows you to put the machine visible as a hard drive on a network. I am sure there are parameters to handle this. Check your machine manuals. Once on the network with proper permissions set, you would be able to copy files to or delete files from the machine from a networked computer directly. No running back and forth with READ and PUNCH commands.