I am looking for advice about tomcat network traffic monitoring system

I am m searching free tools for tomcat network traffic monitoring. I am currently using a lambda probe on Tomcat but it seems that lambda has been always down. Does anyone here have something good comments to share?
If I may just add, that in lambda there are some info available only if tomcat is instrumented with JMX – which I have no knowledge of. Is this a good idea to spend time and learn about it?
Thanks everyone.
