Maybe you should slow down the ping interval a bit, because there is no authentication and someone might run it on a big number of IPs of the same network class, and that will quickly get your IP banned on routers. No one really needs to check the server every 5 seconds (not on free service at least). Perhaps you can make a burst of 4-5 pings every minute or 5 minutes, that would be quite sufficient IMHO, and would significantly reduce your traffic and expenses.