A friend of mine has a Zebra label printer. When connected to one of her laptops it prints out normally but when connected to another (which she wants to use) it inserts blank labels between printed ones. Everything is set up the same way on the two and she has already tried 'everything' to fix it - in particular varying the settings.
I suggested intercepting the messages sent from the two laptops and seeing which bits have had their values switched. Could Arduino be used to record the data being sent so we can analyze it, similar to how you can intercept internet data and read unencrypted traffic? If so, how would I go about doing this?