mod_cluster hits "java.lang.NumberFormatException: null" error on JBoss

Issue

• We do not have proper connectivity between httpd and JBoss via mod_cluster and JBoss has recurring errors like below:

ERROR [org.jboss.mod_cluster.undertow] (UndertowEventHandlerAdapter - 1) null: java.lang.NumberFormatException: null
        at java.lang.Integer.parseInt(Integer.java:542)
        at org.jboss.modcluster.mcmp.impl.DefaultMCMPHandler.sendRequest(DefaultMCMPHandler.java:713)
        at org.jboss.modcluster.mcmp.impl.DefaultMCMPHandler.sendRequest(DefaultMCMPHandler.java:428)
        at org.jboss.modcluster.ModClusterService.status(ModClusterService.java:464)
        at org.wildfly.mod_cluster.undertow.UndertowEventHandlerAdapter.run(UndertowEventHandlerAdapter.java:169)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:750)
        at org.jboss.threads.JBossThread.run(JBossThread.java:320)