I've been trying to trigger the mod's 'OnClientCommand' event hook for multiplayer listen server since many hours ago but it just wouldn't work. Therefore canceled until someone can teach me how to do server-client communication for multiplayer game hosted through listen server.

For any experienced modders who can help me:

When I mentioned 'listen server', I mean hosting multiplayer game through the game itself. Not the dedicated server. And, I didn't attempt the same tests on dedicated server yet.

So, what I did is execute 'sendClientCommand(mod_id, command, args)' from 'lua/client' folder through 'OnPlayerUpdated' event for the listen server mod loading order (shared -> client -> server) and hook the 'OnClientCommand' event from any of the three lua folders. The 'Client', 'Server' and 'Shared' folders. The hook was not called at all so I can't progress from this point onward since the server can't receive command from client.

Not being able to trigger the hook is one thing. Not being able to detect if you are executing code from server side while hosting listen server is another problem. These two problems rendered my reference articles outdated AF. API used to detect if client is hosting server would be 'isServer()' and 'isClient()'.

References:
https://steamlists.com/project-zomboid-client-server-concept-script-guide/
https://theindiestone.com/forums/index.php?/topic/15256-multiplayer-coding-questions/

If there's any modder who can still trigger 'OnClientCommand' hook by hosting current version of listen server, please teach me haha. Otherwise I can't add any feature involving server-client communication in the future which sucks for me.