I'm trying to write .protocol file for dc client but i'm completely failed

Where can i find some docs about it?

You may wish to look here:
http://developer.kde.org/documentation/ ... rency.html

I am not sure if this is up to date though, you may wish to ask in #kde-devel on Freenode if this doesn't work, or look at the contents of the other *.protocol files for further info.

I apologize for replying to this thread of 2 years. However my query is exactly the same. I cant find any info on the KDE protocol files. I wish to create a new protocol to handle magnet links from Chrome.

Unfortunately a search doesnt bring useful info. Also there arent any default .protocol files in ~/.kde/share/kde4/services. There are just .desktop files. The only thing which has a hit on find, is ./share/apps/kopete/urls/Kopete::Protocol

Can someone direct me to any kind of documentation on these files?

Magnet protocol files have been dealt with on this forum before. You will need a minimum of KDE 4.9.3, as bug fixes are required for magnet: urls specifically to function.

Please see viewtopic.php?f=18&t=107938&hilit=magnet+protocol for more details. You want to create a scheme handler in this case. *.protocol files are for KIO slaves only.