Communicate with plc through Android

I want to connect my android device with s7 plc through router to send and receive data. I am new to plc and now its been two weeks of searching for the right source or information but has no luck yet.
I found libraries like libnodave, s7Communication which are used for this purpose but these have no documentation of how to use with android.

If there is no open source library for Android and plc communication please tell me how plc communication works. what protocols or method is used for communication or how can I build my own library?

I am really stuck please help!!
Thank you

I have no experience with Siemens, but for doing the same with a Beckhoff PLC Modbus TCP was the easiest way to go.

Search for Moka7 library, .. or if you want a working Android HMI try this app it communicates with S7 and also with other protocols

Thanks for suggestion @lfe
Does moka7 support communication over wifi ( WLAN ) ?

If you ask that it means you still have a lot to learn about IP, TCP connections and sockets, and you should learn this before trying to implement the library

For your future application to communicate with an S7 system it have to establish a TCP connection and it does not matter through what physical medium is established, for example through WiFi, mobile telephony network, cable or fiber optics.

Yes lfe, I am a newbie in this. Thank you so much for giving me the correct advice.
First, I am going to learn about socket programming them I will go to implementation
Thank you so much for the help!