Companion Disconnected Error

When trying to emulate to companion app no longer connects, we have a firewall rule setup to go out over TCP port 8001 this used to work this no longer works

it works when open it to all ports so wondering if the port it goes over has chnaged?

See the School Setup posts in

Hi Have looked at that and only port mentioned is 8001 and wed had that enabled originally and it has stopped working now so must be using other ports also

This advice might help. It shows all the ports that might be necessary in the section on check list

Which emulator are you using? The MIT_App_Inventor_Tools_30.265.0_win_setup64.exe (~1.5 GB) or the original light weight emulator?

The Companion start screen has a Legacy Connection check box.

Does it have any effect?

just tried it and it does work with the legacy connection option ticked what is the difference in the connection types?

See the latest release notes.

have looked at the latest notes it says it is now using only https have allowed https between the PC and companion and still getting the disconnection

you previously said it works using the Legacy connection, what changed? Are you still using the Legacy connection and it still fails?

The note that says

  • ai2-test now served exclusively with HTTPS

does NOT apply to the main app Inventor server, only the test server. The main server is still http.
Yes, this documentation is confusing. :cry:

For your network people:


  • Firefox 3.6+ -or- Chrome 4+

Whitelist (browser access)






Whitelist port 80 and port 443 to (note: the IP address for can change over time)

Direct (legacy) connection between devices on WIFI, computer and phone. (Port 8001 on the phone/tablet needs to be accessible)

Computer and device access to on port 19302 and on port 3478

Setup Tools requires aiStarter.exe to listen on port 8004

Device/emulator access to on port 6381

Whitelist emulator.exe in computer firewall to access and (needed for downloading app updates)

Windows Only: device drivers for specific android devices, as needed.

(Copied and pasted ugly style from the doc)