When using DCC send in passive mode the sender listens on a local port (59 by default) and sends the receiver a CTCP message (an IRC protocol PRIVMSG message wrapped in \x01) containing their IP address in integer format and the port number. If the receiver accepts their client connects to the sender's open socket and the file is immediately dumped through the connection.
In theory there must be some scheme for forwarding the port through a firewall on the sender side, which might be setting the sending device as "DMZ". Or you can put the burden on the receiver by using active mode.
mIRC should really support UPnP by now but I don't think it does?
In theory there must be some scheme for forwarding the port through a firewall on the sender side, which might be setting the sending device as "DMZ". Or you can put the burden on the receiver by using active mode.
mIRC should really support UPnP by now but I don't think it does?