NICE DCV behind Nginx reverse proxy, "Failed to communicate with server."

Question

I have Nginx running on an Amazon Linux EC2 instance. It is listening for connections to `https://dcv01.example.com` and then using `proxy_pass` with a wildcard cert to serve the DCV client from an internal IP address.  The page displays properly with no SSL errors. However, instead of the login prompt, I get a red message that says "Failed to communicate with server.".

I attempted to use the `allowed-http-host-regex` with the value `^(www\.)?dcv01\.example\.com$`, but then I get a 403.
I also tried `allowed-ws-origin-regex`, but it does nothing different (still get Failed to communicate...)

What do I need to do to get DCV working behind a reverse proxy?

Accepted Answer

I realized this was due to websockets not being proxied.  Adding the following to my server block fixed the issue.

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

NICE DCV behind Nginx reverse proxy, "Failed to communicate with server."

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