Getting Exception while Starting Keycloak in Production

Hello everyone,

I am new to keycloak and we have deployed keycloak in one of our Linux Server. We have simple setup the desired things in keycloak.conf file and able to start as well. However, in the console logs we are continuously getting the below error and it is frequently coming in every 2 seconds.

Recurring exception:

2023-06-16 16:31:27,023 ERROR [org.jgroups.protocols.UDP] (mcast-receiver-6,e3e-11-222-65010) JGRP000030: e3e-11-222-65010: failed handling incoming message: java.lang.IllegalArgumentException: invalid magic number 256; needs to be in range [0…100]
at org.jgroups.conf.ClassConfigurator.create(
at org.jgroups.util.Util.readSizeStreamable(
at org.jgroups.ObjectMessage.readPayload(
at org.jgroups.BaseMessage.readFrom(
at org.jgroups.protocols.TP.handleSingleMessage(
at org.jgroups.protocols.TP.receive(
at org.jgroups.protocols.UDP$
at java.base/

Usually that happens when there’s another keycloak (of a different version) on the same network that is trying to communicated via jgroups/infinispan.

Thank you for your response, this is the only version (keycloak-21.1.1) I have deployed in the server. Plus there is no other keycloak instance running as well.

Gotcha. Thanks for the confirmation. That exception indicates there is an incoming packet over the network to the JGroups port that is unexpected and cannot be processed. I have only ever seen it when there is another keycloak of a different version somewhere on the same network that can be reached by multicast. When you figure out what it is, please post here!