Hi Francis,

Many thanks for your message and for your help, it’s very kind of you.

As you suggested, I’ve tried to add these lines on the “black box” side:

proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection upgrade;
proxy_http_version 1.1;

But unfortunately, without success, these lines didn’t improve the websocket connection. So, I’ve decided to roll back to previous version without the connection upgrade on the “black box”.

I’ve tried different changes to the setup and I finally found my mistake, on the server side I’ve added an extra slash at the end:
proxy_pass https://192.168.1.20:80/;
I change this line with:
proxy_pass https://192.168.1.20:80;

Now, it works smoothly.

The evil always comes from details…

Thanks again Francis for your time and your assistance,

Regards,
YAGA