I've been working on converting IP65, a commodore/apple II ethernet implementation over to the Atari. So far its been going very well. IP65 is in assembler, and once I got over the learning curve it's been proceeding rapidly. Attached to this message is a Real Dos ATR that has a test executable for pinging. If you could try running it on your dragoncart and letting me know of any problems I would appreciate it.
Program name : ping.com
Arguments : its called with the ip or dns name to ping and a iteration count. If you don't provide the iteration count it will default to 4. For example :
ping.com www.atariage.com 10
would ping atariage.com 10 times.
It expects your dragoncart to be at $D500, and your local network to be DHCP-enabled. It makes a DHCP call to get an ip, then it resolves the dns name or ip you've provided and starts sending pings. This is strictly just a test, the final version would be more flexible.
IP65 has a pretty solid implementation, and it has support for telnet and various other TCP programs. Plus, it produces normal Atari exe's that will run under any DOS ( ie., you don't need contiki). You can find the original source and documentation at
http://ip65.sourceforge.net/. I have not added the atari development branch back into that source tree yet.