java gateway : No value for conn

[jolypas]

Hello

I have installed and configured zabbix-java-gateway

I have following exception in zabbix-java-gateway.log

2018-03-04 15:11:29.925 [pool-1-thread-1] WARN  com.zabbix.gateway.SocketProcessor - error processing request
com.zabbix.gateway.ZabbixException: org.json.JSONException: No value for conn
        at com.zabbix.gateway.JMXItemChecker.<init>(JMXItemChecker.java:72) ~[zabbix-java-gateway.jar:na]
        at com.zabbix.gateway.SocketProcessor.run(SocketProcessor.java:58) ~[zabbix-java-gateway.jar:na]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1152) [na:1.7.0_151]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:622) [na:1.7.0_151]
        at java.lang.Thread.run(Thread.java:748) [na:1.7.0_151]
Caused by: org.json.JSONException: No value for conn
        at org.json.JSONObject.get(JSONObject.java:354) ~[json.jar:na]
        at org.json.JSONObject.getString(JSONObject.java:510) ~[json.jar:na]
        at com.zabbix.gateway.JMXItemChecker.<init>(JMXItemChecker.java:57) ~[zabbix-java-gateway.jar:na]

in forum I just found an anwser : "update gateway" but I have the last release I think :
zabbix-java-gateway/trusty,now 1:2.2.2+dfsg-1ubuntu1 all [installed]



the tomcat8 to monitor is on another server,
I have the java-gateway on zabbix server and tomcat server (+ zabbix-agent on it)

any ideas