Not your usual 503 (Virtual Radar Server)


Challenging issue relating to a 503 error which I’m pulling my hair out with.

HAProxy version 2.8.3-86e043a on PFSense.

Believe everything is setup correctly as I have several other websites working perfectly utilising LetsEncrypt and the well regarded Lawrence Systems YouTube guide. These include a Wordpress site along with an Unraid server etc.

The one website I’m having issue with is operating on a non-standard port and http. The website returns fine when browsing direct to the IP internally but ‘503s’ when attempting to access via FQDN.

As a test, I’ve changed the front-end rule to direct to a different backend website and this works. Thus, I assume proving that the front-end is working fine.

The back end is a Mono web service and has an option for defining a ‘Proxy type’…none of the options work. The service is a ‘Virtual Radar Server’ (

The site requires browsing to /VirtualRadar rather than just the FQDN

Curl -I to https://FDQN/VirtualRadar provides the following:

< HTTP/1.1 503 Service Unavailable
HTTP/1.1 503 Service Unavailable

If I Curl -I to the internal IP address, I receive

I receive:

< HTTP/1.1 302 Found
HTTP/1.1 302 Found
< Location:
< Server: Mono-HTTPAPI/1.0
Server: Mono-HTTPAPI/1.0

Any ideas? Is this a Header issue of some sort? The DNS is certainly set correctly and the FQDN is set to the IP address of the LAN port of the PFSense platform. Further, other than the 503, the configuration is reflective of other sites which are working perfectly. I have had this working with NGINX and not had these issues.

Anything further I could check or log to ascertain what may be failing here?

Thank you so much.