This seems to be correct API. Is the metrics collector installed on the same host? (192.168.56.101), 6188 is the default port for AMS. If you have Ambari, you can search for timeline.metrics.service.webapp.address in Metrics collector configs, alternatively you can search for this property in ams-site.xml in the node where it's installed.
Or there's a problem in running collector daemon, you can check
/var/log/ambari-metrics-collector/ambari-metrics-collector.log/out to check it.