COmpanion COnnection Error

My students are using the iOS Companion App to try and connect to the AppInventor website. A lot of them are receiving an error that says Companion Connection Error. We did the same project yesterday and no error. Could it be the internet connection or something buggy with the Companion App. Anyone running into the same problem?


Are you using the Chrome Browser? I am finding the same issue and have narrowed it down to an update in Chrome. This has happened before. Hope they fix it soon.

Yes I am, anyone tried in Microsoft Edge? The weird thing is it is not happening to all my students, my guess is those chrome browsers have not been updated?

  • I am using Android with a fast Internet connection and have experienced slow and incomplete builds this morning. This could be a heavy server load. MITs load balancers frequently sort this out fairly rapidly.

Try Firefox if you can. Microsoft Edge still has strange issues with App Inventor builds on Android. Do try Edge but I guess you might have better results with Firefox.

Two things to check:

  1. Make sure that the students are accessing App Inventor over HTTP and not HTTPS. The older companion connectivity that the iOS version uses will not work when connected via HTTPS. This will be rectified in a future release. Chrome tends to be the most aggressive at enforcing these types of security changes.
  2. Check with your school IT to make sure that the school network is configured to allow the computers running the browser to talk to the iOS devices on port 8004. If this port is blocked, the network connection will always fail.

Is this still happening? We put in a patch that should make Chrome 94 work (again).

Hi there !
Sorry but I have the same issues.
My students who's got an Iphone, there's always Companion Connection Error.
The browser has nothing to do with this. I tried many of them.
But with an Android, it works !!
Could you please solve this ? Any help ?

Android uses WebRTC by default which will attempt multiple ways to negotiate a potential connection whereas iOS expects that the browser will talk to it on port 8001. In Android, that mode is activated when you check the "Use legacy mode" option.

Since it sounds like you're in a school environment, you will probably want to talk to your IT about allowing connections between the computers and the iOS devices on port 8001. There is also this document that we've made available for IT departments to help understand what ports are needed to make App Inventor work in their restricted network environments: