I want to link at least 4 8x8 led dot matrices.
This is pretty common. Adafruit sells everything and has sample code. Copied stuff is available from China if you are on a strict budget, but quality may suffer and compatibility is not guaranteed to the Adafruit software.
http://www.acgears.com/home-office/kits-and-projects/16x32-rgb-led-matrix-panel?gclid=CNaL6471wb0CFUYV7AodbVAAaQ
Ray