Monitoring Apache Kafka via JMX

[hac3ru]

Hello,

I have an apache Kafka container to which I've set the following environmental vars:

      KAFKA_JMX_OPTS: "-Dcom.sun.management.jmxremote=true -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Djava.net.preferIPv4Stack=true -Dcom.sun.management.jmxremote.rmi.port=9999"
      KAFKA_JMX_PORT: 9999

and obviously, I'm exposing port 9999 to the host.
I've got a zabbix server container, frontend, db and I've started a Java gateway, configured the Zabbix server to see the gateway, all good. The only issue is when I try to read something from / via the JMX, because I'm getting an error on the Java gateway console saying:

2025-10-28 16:40:36.075 [pool-2-thread-5] WARN  com.zabbix.gateway.SocketProcessor - error processing request, item "jmx["kafka.server:type=ReplicaManager,name=UnderMinIsrPartitionCount","Value"]" failed: SSL peer shut down incorrectly: service:jmx:rmi:///jndi/rmi://10.3.82.30:9999/jmxrmi
2025-10-28 16:41:39.126 [pool-2-thread-1] WARN  com.zabbix.gateway.SocketProcessor - error processing request, item "jmx["kafka.server:type=ReplicaManager,name=UnderReplicatedPartitions","Value"]" failed: SSL peer shut down incorrectly: service:jmx:rmi:///jndi/rmi://10.3.82.30:9999/jmxrmi
2025-10-28 16:42:33.970 [pool-2-thread-2] WARN  com.zabbix.gateway.SocketProcessor - error processing request, item "jmx["kafka.server:type=BrokerTopicMetrics,name=BytesOutPerSec","Count"]" failed: SSL peer shut down incorrectly: service:jmx:rmi:///jndi/rmi://10.3.82.30:9999/jmxrmi
2025-10-28 16:42:38.284 [pool-2-thread-4] WARN  com.zabbix.gateway.SocketProcessor - error processing request, item "jmx["kafka.server:type=BrokerTopicMetrics,name=BytesOutPerSec","Count"]" failed: SSL peer shut down incorrectly: service:jmx:rmi:///jndi/rmi://10.3.82.30:9999/jmxrmi
2025-10-28 16:42:42.191 [pool-2-thread-3] WARN  com.zabbix.gateway.SocketProcessor - error processing request, item "jmx["kafka.controller:type=KafkaController,name=TopicsToDeleteCount","Value"]" failed: SSL peer shut down incorrect
2025-10-28 16:43:09.111 [pool-2-thread-1] WARN  com.zabbix.gateway.SocketProcessor - error processing request, item "jmx["kafka.server:type=BrokerTopicMetrics,name=BytesOutPerSec","Count"]" failed: SSL peer shut down incorrectly: service:jmx:rmi:///jndi/rmi://10.3.82.30:9999/jmxrmi

I'm already bashing my head at this for the last two hours, so any help would be greatly appreciated.

Thank you!