I also encountered this problem. For me it happened when I was running multiple Unity instances at once on a single Jenkins node what the Jenkins agent was running as Windows Service.

The problem turned out to be that my Windows Desktop Heap Size was too small. I worked around it by increasing the Windows Desktop Heap Size, following the advice here -- https://stackoverflow.com/questions/17472389/how-to-increase-the-maximum-number-of-child-processes-that-can-be-spawned-by-a-w/17472390#17472390 (which I found here -- https://answers.unity.com/questions/1430683/failed-to-get-socket-connection-from-unityshaderco-2.html ).

I also encountered this problem. For me it happened when I was running multiple Unity instances at once on a single Jenkins node what the Jenkins agent was running as Windows Service.

The problem turned out to be that the amount of Windows Desktop Heap available to services, as opposed to applications, was too small. I worked around it by increasing the Windows Desktop Heap size for services on my node, following the advice here -- https://stackoverflow.com/questions/17472389/how-to-increase-the-maximum-number-of-child-processes-that-can-be-spawned-by-a-w/17472390#17472390 (which I found here -- https://answers.unity.com/questions/1430683/failed-to-get-socket-connection-from-unityshaderco-2.html ).

I'm getting this problem when running multiple Unity instances at once on a Jenkins node when the Jenkins agent is running as Windows Service.

I'm working around it by following the advice here -- https://stackoverflow.com/questions/17472389/how-to-increase-the-maximum-number-of-child-processes-that-can-be-spawned-by-a-w/17472390#17472390 (which I found here -- https://answers.unity.com/questions/1430683/failed-to-get-socket-connection-from-unityshaderco-2.html ) -- to increase the Windows Desktop Heap Size.

I also encountered this problem. For me it happened when I was running multiple Unity instances at once on a single Jenkins node what the Jenkins agent was running as Windows Service.

The problem turned out to be that my Windows Desktop Heap Size was too small. I worked around it by increasing the Windows Desktop Heap Size, following the advice here -- https://stackoverflow.com/questions/17472389/how-to-increase-the-maximum-number-of-child-processes-that-can-be-spawned-by-a-w/17472390#17472390 (which I found here -- https://answers.unity.com/questions/1430683/failed-to-get-socket-connection-from-unityshaderco-2.html ).