Bi-directional printing on port 9100

My company just bought a few Canon network printer/copiers which are suppose to support bi-directional communication between workstation and printer through an LPR port and port 9100 on the printer. They want me to test to see if the bi-directionalcommunication works. Any ideas on how to do that? I was thinking of a network sniffer, but even still where to go from there?
Thanks in advance.