Well the title more or less describes my question.
I have two arduino boards, both with the wifi shields, which are currently communicating with cosm(pachube). This part works fine and the feeds are running as they should. What I am interested in doing is having each board react when the other board sends a new value to its feed. I know it's possible through a server using API's and POST/GET requests or something along those lines, but I was thinking if it's possible to simply send a ping to the other board's IP address and have it react to the ping? That would make my life a lot easier as I'm not that skilled at the server side of things.