You are right, there is an issue with how ports are being parsed. By design, when mIRC does not see a "port" specified after the address, it uses the DCC server port by default. What is happening is that the port number specified after the address is not being parsed correctly, so it uses the default DCC server port. It looks like this happened around the time IPv6 support was added, which required extra parsing to determine the address format but broke the port parsing. Thanks for looking into it. This issue has been fixed for the next version.
