So I made this using a Node.JS WebSocket server and HTML5 canvas. It used v3 of my "Elemental Engine" for the front end, which the latest (4.0) can be found here (https://github.com/wg4568/Elemental-Engine-v4.0)
The server is very minimal, and it is very easy to cheat. Fun side project would be to make a "hacked client" in a forked repl.
You also might want to play it here, https://tanks--wg4568.repl.co in fullscreen because the embedded player is very small.
Also, you can find the server here (https://repl.it/@wg4568/TankServer)
UPDATE: bullets will now bounce once on collision with a wall