Hi All. I have created a simple guide to setting up a log4j socket server.
Log4j has a class called org.apache.log4j.net.SocketServer. This class is capable of receiving log messages over a socket and processing them through any of the supported Log4j Appenders. In my example I show how to use the SMTPAppender, and I setup a log4j socket server on my unix box to listen for log messages and process them. All of your clients, or tomcat servers in your case, could then send their messages to the central log4j socket server.
Its pretty easy to do, checkout my writeup at: