Tomcat console access

 For Tomcat v8.5.4 and above, the file <tomcat>/webapps/manager/META-INF/context.xml has been adjusted:

<Context antiResourceLocking="false" privileged="true" >
    <Valve className="org.apache.catalina.valves.RemoteAddrValve"
         allow="127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1" />
</Context>

Change this file to comment the Valve:

<Context antiResourceLocking="false" privileged="true" >
    <!--
    <Valve className="org.apache.catalina.valves.RemoteAddrValve"
         allow="127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1" />
    -->
</Context>

After that, refresh your browser (not need to restart Tomcat), you can see the manager page.

Multiple Tomcat Instances

https://dzone.com/articles/run-configure-multiple-instance-in-a-single-tomcat

https://crunchify.com/how-to-run-multiple-tomcat-instances-on-one-server/