Multiplayer using simple file sharing

I am creating a game, similar to Tetris, where a player sees two grids - his own and his opponent's. To make this multiplayer, I read up on UNet as well as Photon. However, my question is as follows:

Idea: To simply write the grid in a text file with my own formatting and share that file over the internet using a URL. Then the opponent downloads the file from the link and updates the grid accordingly.

Is this a smart way to do this? If so, how should I go about it?
If not, how do I achieve it?