The Java GUI is an applet, working from a client computer, and connecting to the SD which it was downloaded from. In order to communicate with the SD, it uses the SD domain- like it is written in the URL field of the browser. (i.e. 18.104.22.168 or qa100.spheradev.com ).
In order for the Java GUI to work properly, the written domain name (URL) must be resolved from both the client machine - where the applet is running, and the SD machine- in both the root and primary VDS environments.
So - if the domain of the SD is "qa100.spheradev.com" it should be resolved (translated into IP) by the machine on which the client is using, the SD machine - with the root user, and the SD machine with the primary VDS (qa100) user. Failing to resolve the URL in either machine/environment will cause a "network connection error" messages appear in the Java GUI.