If you want to build a cluster using Apache TomEE nodes, you need to edit the $TOMEE_HOME/conf/server.xml file. Then, find this line:

<Engine name="Catalina" defaultHost="localhost">

Insert a child node, like this:

        <Cluster 
         className="org.apache.catalina.ha.tcp.SimpleTcpCluster"
                       channelSendOptions="8">

                <Manager 
                className="org.apache.catalina.ha.session
                         .DeltaManager"
                         expireSessionsOnShutdown="false"
                         notifyListenersOnReplication="true"/>

                <Channel 
                 className="org.apache.catalina.tribes.group
                 .GroupChannel">
                  <Membership                     
                  className="org.apache.catalina
                 .tribes.membership .McastService"
                              address="228.0.0.4"
                              port="45564"
                              frequency="500"
                              dropTime="3000"/>
                  <Receiver className="org.apache.catalina.tribes
                  .transport.nio.NioReceiver"
                            address="auto"
                            port="4000"
                            autoBind="100"
                            selectorTimeout="5000"
                            maxThreads="6"/>

                  <Sender className="org.apache.catalina.tribes
                  .transport.ReplicationTransmitter">
                    <Transport className="org.apache.catalina.tribes
                   .transport.nio.PooledParallelSender"/>
                  </Sender>
                  <Interceptor className="org.apache.catalina.tribes
                 .group.interceptors.TcpFailureDetector"/>
                  <Interceptor className="org.apache.catalina.tribes
                  .group.interceptors.MessageDispatchInterceptor"/>
                </Channel>

                <Valve className="org.apache.catalina
                .ha.tcp.ReplicationValve"
                       filter=""/>
                <Valve className="org.apache.catalina
                .ha.session.JvmRouteBinderValve"/>

                <Deployer className="org.apache.catalina
                .ha.deploy.FarmWarDeployer"
                          tempDir="/tmp/war-temp/"
                          deployDir="/tmp/war-deploy/"
                          watchDir="/tmp/war-listen/"
                          watchEnabled="false"/>

                <ClusterListener className="org.apache.catalina
                .ha.session.ClusterSessionListener"/>
        </Cluster>

This block will set up your server to run in a dynamic discovery cluster. What this means is that every server that runs in the same network using this configuration will become a new member in the cluster and so will share the alive sessions.

All these parameters are so important, so I really recommend you to keep all of them unless you are absolutely sure of what you are doing.