You can check if the DCC Server is working correctly by following these steps in mIRC:

1. Open the Options/Connect dialog. Enter a nickname and alternative nickname.
2. Open the Options/DCC/Server dialog. Make sure all boxes are checked and the port is set to 59.
3. Press the OK button to save the settings and close the Options dialog.
4. In the same copy of mIRC, type the command "/dcc chat" and press the enter key. This will make your copy of mIRC connect to its own DCC Server to chat.

That said, you really want to use an IRC server as that is what mIRC was designed for. The DCC Server is just a basic one-to-one direct chat method.

Some servers, like UnrealIRCd, distribute default configuration files that force you to read through them to make sure that you enable/disable/change various settings, for security reasons, before the server will allow incoming connections. It can take some work and requires some experience with IRC and IRC servers.

Other servers, like Oregano, come with preset configuration files that will work out of the box by following a few simple steps. However, if you plan to use such a server, you need to configure it properly to make sure it is secure for general use.