How to solve the problem (111: Connection refused) while connecting to upstream?

Question

Ruby on Rails

Hello.
What is the point: there is a virtual machine where a domain name is registered. But it was impossible to put ruby ​​on a virtual machine, so the domain name is stored on a virtual machine, and the site itself corresponding to this domain name is stored on a dedicated line on a different machine. - How it is implemented: it's just that in the A-record, the server of the dedicated machine is written in the AT THE VIRTUAL.
I don't know if I should have written it or not.
But 3-4 days ago I go to the site, and there is a 502 error. I restarted the site, but I don’t understand why this happened. The error in the logs is:

/shared/tmp/sockets/puma.sock failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.x.xx, server: sitename.com

Thanks everyone for the replies.