viperet rights. Maybe now there are some standard protocols, but in 2001 I tried to make one device based on the old scanner. There he had his own undocumented Protocol. I can advise you to do the following:
1. First find the documentation under the scanner which will be more accessible and real at the scanner and rush to write. On ebeye'll find the old scanner easily
2. Catch LPT traffic and try to analyze the commands. But it's not the easiest way.