How to set up a multiplayer game?

Question

PHP

Planiurem to develop a multiplayer game in the form of a space shooter. The question arises how to build a multi-user engine. We know how to develop a single player game, but how to make a multiplayer mode remains the question. We make games based on Construct.
I would be grateful if you share your experience in developing multi-user engines. Perhaps there are ready-made solutions for this.

Answer 1

We make games based on Construct.

Why do you need to develop engines if you use constructors? And, to start developing engines, you need to develop just games without constructors.
Continue on construct, there is also multiplayer

Answer 2

Third party baas? gamesparks playfab etc