primitive-cloud-server

A primitive Node server for Scratch 3.0 cloud variables; it's not made for large-scale projects and can easily be tricked by those pesky JavaScript programmers.

Video tutorial:

1. You'll need to have Node installed first.

2. git clone https://github.com/SheepTester/primitive-cloud-server.git
   cd primitive-cloud-server
   npm install
   npm start

This makes a local WebSocket server available at ws://localhost:3000/ and an HTTP server at http://localhost:3000/.

Cloud variables get stored in the cloud-vars/ folder.

You can pass a few command line arguments; do npm start -- --help for a list.

Updating

You can update to a new version by doing

git stash
git pull
git stash pop
git checkout --theirs -- .
git reset HEAD
npm install

This "stashes" your local changes, pulls (downloads) the new files from GitHub, then tries to bring back the files from the stash. This might cause issues, so this then checks out "their" files ("their" refers to the stash that you're bringing back). For some reason, Git might get confused after this, so we just unstage all the files. Finally, it installs new dependencies from NPM.

Details

All WebSocket messages are JSON strings; the server may send multiple JSON objects separated by a newline character, but the client may not do that back.

When the client first connects to the server, Scratch sends a "handshake" message, which I think lets the server know which project it is on so the server can then send a series of "set" messages to initialize the client's cloud variables.

// client -> server
{ "method": "handshake", "project_id": "104" }

// server -> client
{ "method": "set", "name": "☁ cool cloud variable", "value": "45643563456" }
{ "method": "set", "name": "☁ epic cloud variable", "value": "10239489031" }
{ "method": "set", "name": "☁ newish variable", "value": "0" }

After that the client can send a "set" message (same structure) to the server, which will broadcast it to the other clients on the project.