'Address Family Not Supported by Protocol Family; Connect' Error

Question:
I have experienced the following error: "Address Family Not Supported by Protocol Family; Connect". How do I solve it?
Solution:

This seems to be an IPv6 connectivity problem. By default, the Java runtime used by Oxygen XML Author prefers to create connections via IPv6, if the support is available. However, even though it is available in appearance, IPv6 sometimes happens to be configured incorrectly on some systems.

A quick fix for this problem is to set the java.net.preferIPv4Stack Java property to true (java.net.preferIPv4Stack=true).

In order to do this, follow this procedure:
  1. Edit the custom_commons.vmoptions file that is located in the Oxygen XML Author installation folder, by adding the Java property java.net.preferIPv4Stack=true, and save it in the same location.
  2. Restart Oxygen XML Author.
  3. Make sure the procedure was successful by going to Help > About > System properties and check that the value of the java.net.preferIPv4Stack property is true.