https://issues.apache.org/jira/browse/AMQ-3614 - Unable to generate unique id when range of ports are blocked - org.apache.activemq.util.IdGenerator. Patch applied with thanks, left the log at warn as unique ids are important and two simultaneous clients could use the same id with this fallback
activemq/trunk/activemq-core/src/main/java/org/apache/activemq/util/IdGenerator.java