You need to run rdesktop or vnc in X, not from the text console.
Before they will connect to the remote machine you need to make sure you can reach that machine over our network.
DISPLAY is the X display the X client is to connect to. You do not need to set DISPLAY when displaying local xclients on the local X server from your aterm.
It sounds to me like you do not have your network properly configured.
To start in text mode, add the "text" boot option in your boot loader's config file.
Please read the book. It explains how to launch X programs when you start the X server.http://tinycorelinux.net/book.html