I am kerfuddled, and google is no longer a friend, as I wore him out.
Running remote astronomy imaging camera with pclinuxos over internet.
Because of issues running the imaging software in Linux, it is running on XP pro for now. (Later I'll get the observatory imaging running on PCLOS using wine or virtualbox).
Over my local LAN, there is no problem running the remote xp computer either with either another XP machine, or PCLinuxOS with rdesktop.
I can pick a random laptop with PCLinuxOS, even WIFI, open a terminal, usually Yakuake, type rdesktop 192.168.1.107 -f and get a perfect full screen of the XP machine on the Linux laptop or box within seconds.
Operating the camera, telescope controls, all perfect as though I was at the XP machine.
Same perfection using a XP home machine to call the remote.
The above works on the local LAN side of my wifi router connected to cable modem.
Now I try to connect to the XP computer on its own DSL line.
Everyone says simply: rdesktop to the isp address of the remote machine.
If I try whatismyisp.com or several other methods, I get for example, 22.214.171.124, or the longer version: pool-12-13-123-124.ptldme.east.myfairpoint.net.
I try rdesktop -f 126.96.36.199, and combinations of all the above, and it does not compute.
Same if I try xp to xp machines.
The PCLinuxOS machine is still on the same router and cable modem as described in the beginning.
The XP machine is now on the Fairpoint DSL, with no router for now.
In some past checks, I saw that port 3389 was being used by xp.
What am I doing wrong? Please no alternatives like use ssh etc, I want this question answered.