So now you have the logger, let's go to the next step.
Another interesting thing that can be done is to analyze the log messages and make them understandable, this will help you in many ways.
a) Keep an easy to search log in order to track down things that happened in your server and might be useful in order to help your users or track down scammers.
b) Implement some kind of per character logging
c) Keep info on who died in PvP and who killed him
etc etc
Not excited with the logging? Want to move on to packet sniffing?
OK , setup your sniffer prog and start by slowly trying to figure out what happens between servers.
For example: Sniff packets being sent to a single server each time, don't monitor all of them together, start by looking for stuff that seem easy to understand and contain some understandable string to help you figure it out. Fortunately , communication between servers is not encrypted
This is not an easy process and unless you are really lucky or highly experienced you will end up looking at hex jargon for hours until you find something that might be a starting point for further investigation.
You can also save the sniffer logs and start searching them for strings displayed in game, this can be helpful too.