How do i connect to my friends server when i have his IP?

Easy answer: you don't (the functionality to connect to non-official servers was removed following abuse).

Tiny bit trickier answer: you modify the client code to connect to his IP rather than doing what it does now.

Hesh.

>_<

I still think we shouldn't use this engine.

Longs answer:

First you have to know that Daimonin is two things in one: One is the Project/Game Daimonin, the other is the 'Engine' Daimonin. The released clients out are for the game Daimonin, so allow only connects to the game servers.

But as the Daimonin-engine (code) is OpenSource, your are free to use it, and do whatever you want to do with it (within the GPL). So just grab the sourcecode from SVN, for Windows get Codeblocks, change the source (its only one line) to connect to your server and recompile. This should work out of the box.
Another way without recompiling would, what i call, local DNS 'Bending'. You could even modify the client executable with a binary editor.