Okay, firewall would explain why the ping is discarded. Although that's a pretty overzealous thing to do for a firewall, take away the easiest and most obvious way to detect if a system is alive and reachable on the net. Some services might even depend on it by sending a ping first before they do more stuff on the net. Dunno if Dom3 is among those.
I have uploaded my server check script here:
http://valhalla.srhost.info/socket.php
It will first connect to Velusion's Fallacy game (so that you can see that the script is indeed working) and then to your server.
You can check if your port 1024 is reachable outside here:
http://www.canyouseeme.org/
http://www.port-scan.de/lynx/select.php
Just enter your port number 1024 in those and submit. Don't mind the German on the second one, you just have to look at the reply. If it doesn't say "open" (which they will display in red, because they check if a firewall works, not a service), then others can't connect to your game.
I know that other people have hosted games behind hardware / software routers, so you could use the search function here.