If like FedoraMike said, you mean "live chat" then the only way that could be accomplished is to parse the log files the server generates when a player types a message. This would require an additional server to store the logs in realtime. This could be done but would quickly drain the resources of the gameserver (Think B3 Bot) and unless you have your own dedicated server most hosting companies will not allow you to use their resources like that because it put a drain on other gameservers hosted on the same system. To summarize, it can be done, but requires a dedicated server with lots of resources to accomplish.
Tesla[1up]