I have an Evisalink 3. It has been working for years. After upgrading a CLIENT computer (not the indigo server) to Big Sur, I started receiving socket errors. I think the OS upgrade is a coincidence.
DSC Alarm Initializing communication at address: 192.168.4.101:4025
DSC Alarm Error Error opening socket: Could not open port socket://192.168.4.101:4025: timed out
DSC Alarm Plugin will attempt to re-initialize again in 3 minutes.
I can still use it with Eyez-On, and I can access it directly from the internal network, and I can ping to it. The exact port, however, is inaccessible.
Set up:
1. Indigo server running on an old Mac mini
2. Evisalink 3
3. Apple AirPort Extreme. Base Station
4. Client indigo on Big Sur