java or python , I know also the basis of php.

Dont use PHP for that ;) Python is always a good language for Networking (Java too, but Python is cuter)

This SO answer should have some directions for you: https://stackoverflow.com/questions/30604192/creating-a-real...

Thank you for the answer, I can use this solution with Google app engine right? I really hate php I try to don't use it at all ! I really don't know if XMPP that is built in google app engine can help us create a chat app or no.

Afaik you could just use the Python implementation. That means you build your bot to a prototype and then look what wrappers you need for GWT. At first try to make your bot, deploying to google should be simple then (in Python at elast)

I understand but really the problem is how I can integrate this webapp with my android app for example in : Google app engine and android=> I can use google endpoints to get data.