Forums mIRC Help How DCC send/receive works?

Esentially, yes. In any mIRC window, type /help dcc server protocol

DCC, Direct Client to Client allows you to connect directly to another user rather than going thru the IRC network so that you can send/get/chat privately over a more secure connection. mIRC allows you to specify the range of ports it will use when making dcc connections (always assuming your firewall/router allows access on those ports)