As far as I know, there are no msgpack-RPC libraries that use GLib. I wanted to build a GTK-based Neovim frontend tailored to my tastes, and for that I would need an API client to talk to the nvim backend. This library would have served as the backbone for communication. But then, I got bored halfway through the project and managed to implement barely functional client/server classes before giving up. I am going to put this up here anyway, in case anyone wants to use the code. There are some tests that demonstrate how the different classes may be used.