Minecraft finds a way.
This is a very alpha-quality Heroku app that runs a Minecraft server on a single dyno.
Since Heroku is a bit of a weird platform, there are a couple of caveats to running a Minecraft server on it.
Since Heroku no longer supports TCP routing, we're proxying the connection through WebSockets. This means each client will have to run a little tool to turn the WebSocket connection back into a regular TCP Minecraft connection. This is detailed below in the "Client" section.
Heroku has no persistant storage, so you will have to have an Amazon AWS account and an Amazon S3 bucket ready to store your world data. Your world data will be automatically synced to and from S3 in the background.
Create a new Heroku app with a custom buildpack.
$ heroku create my-app-name --buildpack https://github.com/ddollar/heroku-buildpack-multi.git
Add your Amazon AWS credentials and S3 bucket name to the Heroku configuration. This enables data persistence. Otherwise, your server will be wiped each time it is restarted.
$ heroku config:add AWS_KEY=xxxxxxx AWS_SECRET=yyyyyyyyyyyyyyyyy S3_BUCKET=my-bucket-name
Push the app to Heroku.
$ git push heroku master
Hopefully, this process can be streamlined in the future, but for now it's a little squirrely if you aren't a developer.
These instructions are for OS X, or some other Linux-like operating system maybe.
Change to the repository you cloned.
$ cd ~/Downloads-Or-Wherever/heroku-minecraft
Install the NPM dependencies.
$ npm install
Run the proxy service. This will proxy the Minecraft server on Heroku to your local machine. The server will appear to be a Minecraft server running on your local machine.
$ coffee proxy/connect.coffee my-app-name.herokuapp.com
Leave the terminal window open and launch Minecraft. Add a new server with the address
localhost. Hit connect and play! When you're done playing, close the terminal window.
Much of the original Heroku setup by Jacob Gillespie.
Updates, refactoring, and the WebSockets proxying by Wil Gieseler.