I have managed this with wi-fi networks. i.e. when I enable wi-fi on my palm and connect to a known wi-fi network, once the palm is connected, on another computer I can ping my palm using "ping palm-webos-device" and ssh into it with "root@palm-webos-device". (My v220.127.116.11 Palm Pre has a hostname of "palm-webos-device", not "castle".) How did I do this: I followed the advice on (because of the dumb restriction on posting links I have to baffle the silly system) https : // calomel . org / dhclient . html, with my own additions. Note that this only works on suitably configured DHCP-based networks with suitably configured computers on the network.)
1. Set your root parition on your palm pre to read-write.
2. Backup then edit the file "/etc/PmWiFiDhclient.conf", adding the lines, in the following order:
send host-name "palm-webos-device";
supersede host-name "palm-webos-device";
request subnet-mask, broadcast-address, time-offset, routers, domain-name, domain-name-servers, host-name;
3. Save the file, and reset the root partition to read-only.
4. Reboot your palm pre (the only way I quickly found to restart the dhclient process on the palm pre, probably other ways, but couldn't be bothered to find out).
Now, using a hostname other than "palm-webos-device" would require editing more files, at least "/etc/hostname" and probably others, which I didn't do.
Once this was done, I installed ssh and the sftp server, and even, on Ubuntu, managed to browse the palm pre's filesystem from another computer on the same-wifi network.
Note that if the palm pre goes to sleep, despite keeping the wifi on whilst asleep, an ssh link to the palm does seem to not respond, which recovers once the palm is awake.