From the Kura side,I get the error below (which is different from the one I get if Kapua is not running, so I suspect the gateway is connecting to the broker). On the Kapua side, i don't know where to look for the broker's log.
2016-12-05 16:14:30,210 [DataServiceImpl:ReconnectTask] INFO o.e.k.c.d.t.m.MqttDataTransport - # willMessage =
2016-12-05 16:14:30,211 [DataServiceImpl:ReconnectTask] INFO o.e.k.c.d.t.m.MqttDataTransport - #
2016-12-05 16:14:30,211 [DataServiceImpl:ReconnectTask] INFO o.e.k.c.d.t.m.MqttDataTransport - # Connecting...
2016-12-05 16:14:30,211 [pool-11-thread-1] INFO o.e.k.c.s.r.LogStatusRunnable - Notification LED fast blinking
2016-12-05 16:14:30,252 [DataServiceImpl:ReconnectTask] WARN o.e.k.c.d.t.m.MqttDataTransport - xxxxx Connect failed. Forcing disconnect. xxxxx {}
Broker unavailable (3)
at org.eclipse.paho.client.mqttv3.internal.ExceptionHelper.createMqttException(ExceptionHelper.java:31)
at org.eclipse.paho.client.mqttv3.internal.ClientState.notifyReceivedAck(ClientState.java:885)
at org.eclipse.paho.client.mqttv3.internal.CommsReceiver.run(CommsReceiver.java:124)
at java.lang.Thread.run(Thread.java:745)