OnCommand Insight - All Data Sources fail acquisition with "Internal Error: Error" message

Applies to

OnCommand Insight (OCI) 7.3.x 

Windows Server 2012 or later

Issue

All data sources fail with 'Internal Error' 

The OCI acquisition log (RAU or Local) '\SANscreen\acq\log\acq.log' shows the following errors:

HTTP transport error: java.net.SocketException: No buffer space available (maximum connections reached?): connect

On the OCI Server's Host OS in '\SANscreen\wildfly\standalone\log\elasticsearch_client.log' you can see the following errors:

2019-10-08 17:35:51,270 ERROR [pool-10-thread-1] ElasticAdminManager (ElasticAdminManager.java:329) - Failed retrieving cluster information, error: No buffer space available (maximum connections reached?): connect
2019-10-08 17:35:51,270 ERROR [pool-10-thread-1] ElasticAdminManager (ElasticAdminManager.java:207) - Failed retrieving cluster information, error: Failed retrieving cluster information
2019-10-08 17:35:51,270 ERROR [pool-10-thread-1] ElasticCommon (ElasticCommon.java:544) - Failed retrieving cluster information
com.netapp.oci.es.ElasticsearchException: Failed retrieving cluster information
    at com.netapp.oci.es.admin.ElasticAdminManager.getClusterInfo(ElasticAdminManager.java:208) ~[elasticsearch-client.jar!/:?]
{Truncated}
    at java.lang.Thread.run(Thread.java:748) [?:1.8.0_172]
Caused by: com.netapp.oci.es.ElasticsearchException: Failed retrieving cluster information
    at com.netapp.oci.es.admin.ElasticAdminManager.getNodesInfo(ElasticAdminManager.java:330) ~[elasticsearch-client.jar!/:?]
    at com.netapp.oci.es.admin.ElasticAdminManager.getClusterInfo(ElasticAdminManager.java:201) ~[elasticsearch-client.jar!/:?]
    ... 10 more
Caused by: java.net.SocketException: No buffer space available (maximum connections reached?): connect