Is there a simple way to test from a PC whether I can log on to a DX that is connected via Ethernet?

You can use the Windows telnet command.

1. Click Start > All programs > Accessories > Command Prompt.
2. At the command prompt, type "telnet. "
3. Given a DX IP address of "10.1.32.130," type the following (the port number is 34260).
   Microsoft Telnet>open 10.1.32.130 34260
4. When E1 402 is displayed, type "admin. " If E0 is displayed, logon was successful.
5. To log off, type "cc0. "

For details on logging on, see Appendix 2, "Logging On " in the communication interface user's manual (IM04L41B01-17E）
User's manual download