Problem of how to trigger the MAX/MSP with UNO

I am doing a project that need to use the button(Digital In on Arduino UNO) to play the video on Max/Msp by serial port communication.

But First time I doing on this and I feel complicate. Does any one know there are any source code or video is seems like the such kind of things?

Thank you so much.

What is the Max/Msp (whatever that is) expecting to receive in order to play a video ?

Just to get you started.

Some of the information is very old so you may have to do more googling to find recent information.