Steps to reproduce:

1. Changes in configuration... -> According to files "zabbix_server.conf, zabbix_java_gateway.conf and zabbix_java_gateway_logback.xml" attached.
2. Navigate to screen title... -> It is not necessary
3. Click on screen element... -> It is not necessary
4. ...

Result:
See screenshot... -> File "jmx_red.png"attached.
See log file... -> File "zabbix_java_gateway.log.zip" attached.
See memory dump... -> It is not necessary

Problem: 
========= 
After completing the installation and configuration of the Zabbix Java Gateway (without having any JMX monitoring configured within Zabbix), the following error messages appear in "zabbix_java_gateway.log" constantly (the log file is growing more and more):
...
...

2018-05-18 14:24:26.057 [main] INFO com.zabbix.gateway.JavaGateway - Zabbix Java Gateway 3.4.8 (revision 79252) has started 
2018-05-18 14:24:26.077 [main] INFO com.zabbix.gateway.JavaGateway - listening on 0.0.0.0/0.0.0.0:10052
2018-05-18 14:25:09.939 [pool-1-thread-1] WARN com.zabbix.gateway.SocketProcessor - error processing request 
com.zabbix.gateway.ZabbixException: java.io.IOException: Failed to retrieve RMIServer stub: javax.naming.CommunicationException [Root exception is java.rmi.ConnectIOException: non-JRMP server at remote endpoint] 
        at com.zabbix.gateway.JMXItemChecker.getValues(JMXItemChecker.java:98) ~[zabbix-java-gateway-3.4.8.jar:na] 
        at com.zabbix.gateway.SocketProcessor.run(SocketProcessor.java:63) ~[zabbix-java-gateway-3.4.8.jar:na] 
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_171] 
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_171] 
        at java.lang.Thread.run(Thread.java:748) [na:1.8.0_171] 
Caused by: java.io.IOException: Failed to retrieve RMIServer stub: javax.naming.CommunicationException [Root exception is java.rmi.ConnectIOException: non-JRMP server at remote endpoint] 
        at javax.management.remote.rmi.RMIConnector.connect(RMIConnector.java:369) ~[na:1.8.0_171] 
        at javax.management.remote.JMXConnectorFactory.connect(JMXConnectorFactory.java:270) ~[na:1.8.0_171] 
        at com.zabbix.gateway.ZabbixJMXConnectorFactory$1.run(ZabbixJMXConnectorFactory.java:76) ~[zabbix-java-gateway-3.4.8.jar:na] 
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[na:1.8.0_171] 
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_171] 
        ... 3 common frames omitted 
Caused by: javax.naming.CommunicationException: null 
        at com.sun.jndi.rmi.registry.RegistryContext.lookup(RegistryContext.java:136) ~[na:1.8.0_171] 
        at com.sun.jndi.toolkit.url.GenericURLContext.lookup(GenericURLContext.java:205) ~[na:1.8.0_171] 
        at javax.naming.InitialContext.lookup(InitialContext.java:417) ~[na:1.8.0_171] 
        at javax.management.remote.rmi.RMIConnector.findRMIServerJNDI(RMIConnector.java:1955) ~[na:1.8.0_171] 
        at javax.management.remote.rmi.RMIConnector.findRMIServer(RMIConnector.java:1922) ~[na:1.8.0_171] 
        at javax.management.remote.rmi.RMIConnector.connect(RMIConnector.java:287) ~[na:1.8.0_171] 
        ... 7 common frames omitted 
Caused by: java.rmi.ConnectIOException: non-JRMP server at remote endpoint 
        at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:248) ~[na:1.8.0_171] 
        at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:202) ~[na:1.8.0_171] 
        at sun.rmi.server.UnicastRef.newCall(UnicastRef.java:338) ~[na:1.8.0_171] 
        at sun.rmi.registry.RegistryImpl_Stub.lookup(RegistryImpl_Stub.java:112) ~[na:1.8.0_171] 
        at com.sun.jndi.rmi.registry.RegistryContext.lookup(RegistryContext.java:132) ~[na:1.8.0_171] 
        ... 12 common frames omitted
2018-05-18 14:26:09.995 [pool-1-thread-2] WARN com.zabbix.gateway.SocketProcessor - error processing request 
com.zabbix.gateway.ZabbixException: java.io.IOException: Failed to retrieve RMIServer stub: javax.naming.CommunicationException [Root exception is java.rmi.ConnectIOException: non-JRMP server at remote endpoint] 
        at com.zabbix.gateway.JMXItemChecker.getValues(JMXItemChecker.java:98) ~[zabbix-java-gateway-3.4.8.jar:na] 
        at com.zabbix.gateway.SocketProcessor.run(SocketProcessor.java:63) ~[zabbix-java-gateway-3.4.8.jar:na] 
... 
... 

The Zabbix Java Gateway log file is attached zipped. ->File "zabbix_java_gateway.log.zip" attached. 

Status of service:

=============

[root@zabbix ~]#
[root@zabbix ~]# systemctl status zabbix-java-gateway
● zabbix-java-gateway.service - Zabbix Java Gateway
Loaded: loaded (/usr/lib/systemd/system/zabbix-java-gateway.service; enabled; vendor preset: disabled)
Active: active (running) since Fri 2018-05-18 14:24:26 -03; 51min ago
Main PID: 1042 (java)
CGroup: /system.slice/zabbix-java-gateway.service
└─1042 java -server -Dlogback.configurationFile=/etc/zabbix/zabbix_java_gateway_logback.xml -classpath lib:lib/android-json-4.3_r3.1.jar:lib/logback-classic-0.9.27.jar:lib/logbac...

May 18 14:24:24 watcher-server-prd systemd[1]: Starting Zabbix Java Gateway...
May 18 14:24:26 watcher-server-prd systemd[1]: Started Zabbix Java Gateway.
[root@zabbix ~]#

The following configuration files are attached: 
"zabbix_server.conf" 
"zabbix_java_gateway.conf" 
"zabbix_java_gateway_logback.xml" 

On the Host Configuration screen, JMX availability is red according to the attached screen -> Look file "jmx_red.png"attached. 

Can you please help me identify and solve the problem? 

I have already accessed and read this "note" ZBXNEXT-1274 but I found nothing in it to help. 

Thank you very much in advance! 

Adriano