Scratch Link connection for hardware extensions should work without Internet access

Expected Behavior

If Scratch Link is running, hardware extensions like the micro:bit, LEGO WeDo 2.0, etc., should work whether or not the computer is connected to the Internet.

Actual Behavior

Connecting to Scratch Link requires an Internet connection: specifically, we need DNS to resolve the device-manager.scratch.mit.edu name to an IP.

Proposal

Scratch Desktop is a different security environment for the Scratch editor, and in particular it can probably be configured to connect to Scratch Link over plain ws:// instead of wss://. In that scenario we wouldn’t need to validate the name on a digital certificate, so we wouldn’t need to connect using a DNS name: we could just connect to ws://127.0.0.1:<port>/ and avoid the need for DNS altogether.

This would require Scratch Link to expose a regular ws:// port in addition to its current wss:// port but that should be easy.

[Timurinyo]

@cwillisf It worked. Thanks for being so helpful!

[y05s]

Hi this is my first post of GitHub. I’m @y05s from scratch3.0 thread, discussing about “scratch link never work on my local network”. https://scratch.mit.edu/discuss/topic/354657/?page=1#post-3597312 I’ve just solved my issue above, and this Github thread was much useful for me. I have to say thank you so much!!!

To prevent security risk, latest DNS masquerade service is rejecting to map to private ip-addresses, such as 192.168.*.* ,127.0.0.1 . The DNS record of device-manager.scratch.mit.edu to 127.0.0.1 matches to this restriction. Please refer following discussion for your more understanding: https://news.ycombinator.com/item?id=12408918

At least a school local network has this secure router configuration, it can be found in scratch3.0 thread, and similar sites would be increasing. Please consider/plan to discontinue using this DNS record. Thank you.