turn based game over long time period

i have an idea for a simple turn based game. i would like to allow for players to stop and continue the game over days/weeks. i would prefer an android game. game progress and player ips could be simply saved in something as simple as a text document or string somewhere. my game could access and reload / connect when players open the game.

i am looking for advice on the simplest way where/how to store the data/string required?

Expect that IP addresses change between runs.

Simple text file methods to use are File.WriteAllText, File.ReadAllText.