Due to probs within routers etc, some ppl use dccserver to send files, they are asking you to enable your dccserver (file/options/dcc/server) on that port by typing that command.
In mIRC, type
/help dcc server and then scroll down. By default dccserver is disabled, and rightly so, since it listens for direct connections rather than thru the network.
I'm sure we will see you again to fix all the trojans and virii you download