servicemix.properties contains settings for ActiveMQ host/port/url:
activemq.port = 61616
activemq.host = localhost
activemq.url = tcp://$
Same time activemq.xml hardcodes the same information:
<amq:transportConnector uri="tcp://localhost:61616" discoveryUri="multicast://default"/>
So if user changes property file (which seems logical) without changing xml file (which might look non logical) to use another port or change localhost to 0.0.0.0 then it will not work.
Problem could be solved by using placeholder in transport connector: