I just spent several days pulling my hair out trying to figure out the Unknown Connection Error issue. I am testing with the latest version of Spark (2.8.3) and the latest version of Openfire (4.3.2).
I tested in both using a docker container and a VM. Initially, I was using the default-jdk and this did not work. When I downgraded to openjdk-8-jre-headless things started working. Anybody else get this experience?
Has the documentation been updated to reflect this? I looked at the docs…there is a mention of java 1.7 being require. Given that the latest version of java is not compatible with Openfire, this should be more prominently displayed (somehow). IMHO.