I have successfully set up the built in MQTT broker and MQTT bridge to control SmartThings devices via Home Assistant. Now I am trying to set up HA as the MQTT broker for Blue Iris. When I try to set it up I get an error 10062, that the raspi and/or HA has refused a connection on the MQTT port. I have looked through tons of posts and docs and I can’t find anything that clearly spells out how to allow for anonymous access from a local LAN connection to MQTT. If someone could help me out I’d appreciate it. I have checked the manual and either it isn’t there or I’m too dumb to understand it, either is just as likely 
I don’t use the embedded broker, but I don’t believe it allows anonymous connections. You have to supply a username and password.
It looks to me like you can maybe hit it on port 8080, but I wound up just using URL calling from Blue Iris instead and that seems to work well. Thanks.