Links to Relevant Wiki Articles(s):
Scratch Link runs a small server on your computer that Scratch in your web browser can communicate with using web sockets.Scratch in your browser can find the server Scratch Link creates at "device-manager.scratch.mit.edu" using port 20111, but it's really just your local machine (127.0.0.1).
Make sure that this url is not being blocked by your content filter and that no other software is using that port. If using a Windows device, you can check if other software is using the port by going to the Start menu → All Programs → Accessories → System Tools → Resource Monitor. If you are using a Mac, use this command to see which process is using the port: sudo lsof -nP -iTCP:5000 | grep LISTEN
In February 2022, we released an important security update to Scratch Link. If you’re having difficulties using Scratch Link, make sure you are running the latest version. You can download the latest version here, or in the Apple or Microsoft app stores.
If you’re using the Scratch App (also known as the offline editor) to connect to physical devices, make sure your Scratch App is updated to at least version 3.29.