How to access a servlet on Tomcat from the internet?

Question

Java

I'm trying to write a client-server application that will show promotional offers from grocery supermarkets. For one supermarket chain, I receive information and save it in a MySQL database. Now the task is to write an Android client that can communicate with a servlet (it will launch a parser and a class for writing to the database) and receive promotional offers for the current day. I have Tomcat installed, but how can I access the servlet from the internet? How to make the client on Android able to get the necessary information?
Thank you.