Newbie: how to talk to NM by C or C++? Need some hints.

["inthawadee C." <nopasdee gmail com>]

Hello all, 

How can I get the current statuses such as signal strength and maximum 
bit rate (also connection status). of wireless access point from NetworkManager by programming in 
C/C++? 
I have read many pages recommended in archives such as 

http://projects.gnome.org/NetworkManager/developers/spec.html#org.freedesktop.NetworkManager.AccessPoint
http://projects.gnome.org/NetworkManager/developers/libnm-glib/08/NMActiveConnection.html#NM-ACTIVE-CONNECTION-SERVICE-NAME--CAPS

but still have no clue how to talk to NetworkManager.  

I just want to use the mentioned parameters as input factors of my experiment implemented in C. 
Previously, I worked with iwconfig and iwlist but want to try the program through Network Manager.

Thanks in advance.

Papagei