I'm making a program with ASP.NET Core with SignalR, and it works fine except in a very specific circumstance, and I can't work out exactly what the cause/fix is:
Everything works fine on all browsers (desktop or mobile Chrome/Firefox) when mobile is connected to WiFi. However if I turn off WiFi on mobile so that it uses mobile data, Firefox for android gets the error Error: Failed to start the transport 'WebSockets': Error: There was an error with the transport. logged in the console when trying to initialise a connection to my SignalR hub. This problem doesn't happen on Chrome mobile.
This is Firefox for Android 68.10.1. Testing on Browserstack, this doesn't seem to happen of V65 (which is the highest version availableI could find there).
I don't think this is an issue with the reverse proxy (nginx in my case) configuration as it works normally on different browsers or when FireFox is on WiFi.
Any ideas what causes this behaviour in these specific circumstances (Mobile data not WiFi, Firefox for Android only), and how to resolve this?
