Based on p5.multiplayer GitHub repository
from p5.multiplayer GitHub repository
Open a terminal window and navigate to the project directory.
Run the command npm install.
Next, run the command node server.js to start a node.js server.
Open a browser and go to http://127.0.0.1:3000/host.html. This will open up a host page. Make note of the URL displayed in the bottom left corner of the screen.
Open a second browser and go to the URL displayed on your host page. It will look something like http://127.0.0.1:3000/?=roomId, where roomId is a randomly generated name. This screen will load a controller that let's you control the movement of a colored square on the host page.
(OPTIONAL) The included node.js server cleverly lets you specify a custom room ID (think of it as a semi-private game room). You can specify your own room ID by opening a host page using http://127.0.0.1:8080/host.html?=roomId, where roomId is a string of your choice.
Launch homepage and setup game
There will be alink presented on the home page. Open a new tab at that link until you have as many tabs as players.
Follow on-screen instruction to play - you don't have to return to the home screen again. It is only used to start a new game.