Adding a server, "failed to ping"

Hi,

My server is behind a hardware firewall and I believe this is causing an error when trying to add it to planetminecraft as I'm getting:

"Failed to ping "X.X.X.X:X". Make sure it is properly setup, port forwarded, online and other people can connect to it.

My server is up and runing, it is accepting players.


I would like to know what IP/domain is used by planetminecraft to ping servers and is it a standard ping (icmp) or are you querying the game server?


Thank you