I have found that uncommenting the following:
<Valve className="org.apache.catalina.valves.AccessLogVal ve"
directory="logs" prefix="localhost_access_log." suffix=".txt"
creates log files of visitors.
You need to add this to the in the section for the relevant virtual host.
Now I have another problem, I want to display the name of the requestor, not just the IP. I tried setting resolveHosts to true, but then could not connect to my site. Any ideas??