How to communicate with plc through android

Hello everyone,
I have few questions to ask.
1. what things (languages, protocols ) we need to learn to create a library like libnodave, moka7 etc?
2. What are the sources through which I can get the deep understanding of communication between plc and android?

Any sort of advice or help is appreciated
Thank you !!

You'll get better results if you post in the 'Live PLC Questions and Answers' portion of the forum. Not many people frequent here.

That said, check out this thread:
http://www.plctalk.net/qanda/showthread.php?t=114977