"Connect directly to Xvnc started by xrdp"
You want to connect to the VNC server that is running on your linux box. By default when you install xrdp the VNC server is setup to accept connection from the local host only. This keeps any potential security problems that the VNC server may expose limited to the localhost only. No external connections.
The VNC server is the 'middle man' here. It connects the xrdp to the X session. Another 'middle man' supported by xrdp is X11rdp.
The information you are looking at here:
The library libvnc is a VNC client.
The username / password:
These are the linux user/password.
Just like logging in locally.
From the xrdp web site:
Libvnc, a VNC module for xrdp. Libvnc provides a connection to VNC
servers. Its a simple client only supporting a few VNC encodings(raw,
cursor, copyrect). Emphasis on being small and fast. Normally, the
xrdp server and the Xvnc server are the same machine so bitmap
compression encodings would only slow down the session.
Sesman, the session manager. Sesman is xrdp's session manager. Xrdp
connect to sesman to verify the user name / password, and also starts
the user session if credentials are ok. This is a multi process /
Linux only session manager. Sessions can be started or viewed from the
command line via sesrun.
Connect to the VNC server used by xrdp.
Determine what VNC server is running on your machine.
One way would be something like:
ps aux | grep -i vnc
Now locate the config file for this server and adjust who can connect to this server. Chances are there is not a password setup.
Each server will be different so I cannot say here.
The takeaway is that you want to change the config file for the VNC server and not xrdp.
Remember to change the VNC server back to localhost only when you are done to prevent any one from connecting the the VNC server directly.