Web Server for AoE 1, 2 and 3 DE supporting LAN multiplayer 100% offline

Classic AoE-playing Hacker News-types might also enjoy 0 A.D.

It's free and fun, but definitely humbling if you consider yourself a master strategist:

https://play0ad.com/

i love 0ad so much but it runs AWFULLY as soon as you get a fun number of units on the map.

I haven't had an issue with that personally (played on and off for almost 10 years), though I imagine it could be an issue on some older hardware. Massed units will cause lag in big team games where there's 4 armies clashing, though that might be more of a network thing.

I am curious as a non game developer, are these types of games deterministic? If so if I send to the server that I moved huge units to attack another huge units, can the server determine what the end will be? Why do we face a network issue?

They can be deterministic but I think you might be confused about the kind of game

In RTS games like 0AD or AoE you don't just send a single huge unit to attack and wait for the result, you send many tens of individual units near enemy units, then the "battle" goes on in real time and you can micromanage units to influence the outcome. You can't just simulate it on the server because the server can't simulate the thought process of the players