Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Valknut is a program that uses the Direct Connect protocol. It is compatible with other DC clients, such as the original DC from Neomodus, DC++ and derivatives. Valknut also interoperates with all common DC hub software. Valknut was originally written by Mathias Küster and is licensed under the GNU GPL. It is written in C++ and uses the cross-platform Qt library for its GUI. Valknut compiles and runs on Linux, FreeBSD, Mac OS X, Microsoft Windows, and OS/2 - eComStation.