Multiplayer online game for novice developers using node.js and Redis
This code is a sample for creating a multiplayer online game for novice developers. The idea is that there's no use of any MMO framework so that it is not a barrier for novice developers. We keep it simple by using only nodejs & Redis. Redis is our state server which keeps the state of all the players in the game. Our servers are stateless, so it doesn't matters to which servers the users are connected. We'll use Redis pub/sub feature to also sync all the servers with all the users' location change updates.
In this scenario we have one big world, which we split to buckets using the spatial-mapping node module. Each bucket is mapped to a specific ID in the world so that we can use a hash to keep mark users are in each bucket. We can also use this key to save this data in a simple database, like Azure Table for example, which cost less than comparable spatial-capable solutions.
In this example the client side is a simulation of how the world appears from an altitude of 30 miles. We can see the players spread in the world, and also our "view" represented as the red border around us. The "view" is the area that is visible to us as players. The blue border around the red one, is an area for which we still get updates, although it is not visible to us. This is for the client logic to know that a player is coming to our direction, or a player is leaving our visible area.
Find more about this in my blog post.
First, you'll need to install Redis locally on your machine, or use Redis as a service (here for example).
Then, enlist the code and run:
git clone https://github.com/amiturgman/nodemmo.git
cd nodemmo/src
npm install
node app.js
Open your favorite browser, and browse to http://localhost:3000.
I used 3000 because I read somewhere on the internet that it was cool.
In the username textbox, type a username and hit the Start button.
Clicking here will trigger a random location-update event beeing sent to the server every second, and propagate to all users connected to one of the servers.
Only users that we're in their visible area- will get the event, and will see us in their view (+extra) area.
In order to see how this is working, there is also a hook which allows you to trigger location-change events by triggering an http request:
Press pause to stop the location change events, and look at the last location change event that was sent to the server by switching to the node console.
Trigger a similar http POST request to http://localhost:3000/location, by replacing the x and y coordinates with nearby coordinates.
After triggering the request you should see the new user located around you in the view. Try playing with the coordinates and move the users further to the view + extra borders (red and blue). You will notice that once you move out of the view, you will not get any location updates anymore.