https://askubuntu.com/questions/234856/unable-to-do-remote-desktop-using-xrdp

On file /etc/xrdp/xrdp.ini add address=0.0.0.0 which is the default xrdp address.

Also you have to permit firewall to listen to connections on port 3389 that xrdp is working on. For this execute:

sudo ufw allow 3389

If that doesn't work either:

1. Restart PCs
2. Disable firewall (sudo ufw disable) on server pc and then recheck (might even need another restart).

In case you missed it, i will list the entire procedure below (which was a pain to assemble). You'll be fine with that if you follow step by step (promise!).

Remote Desktop between any OS's Step-By-Step guide

I. Windows to / from Windows:

Use Windows Remote Desktop software

II. Linux / Unix to / from anywhere

First do the following on the server computer that you will connect via remote desktop:

- Allow other users to view your desktop
- Best to require a password
- service ssh status
- To allow computers to connect with X11 graphics system capabilities as well, you need to 
    install an X11 server on the computer that is trying to connect (client). So
    * for a Windows computer use XMing
    * for a Linux Ubuntu computer use XQuartz

IIa. Windows to Linux from terminal with graphics support

- Launch XMing on Windows client
- Launch Putty
    * Fill in basic options
    * Connection -> SSH -> X11
        -> Enable X11 forwarding
        -> X display location = :0.0
        -> MIT-Magic-Cookie-1
        -> X authority file for local display = point to the Xming.exe executable

IIb. (b for better) Windows to Linux with full GUI support. This is what most of you will want.

- install xrdp which uses the remote desktop protocol to present a GUI to the user. 
    It can provide a fully functional Linux terminal server, capable of accepting connections 
    from rdesktop, freerdp, and Microsoft's own terminal server / remote desktop clients. 
    xrdp is the daemon that handles RDP remote desktop access from Windows machines to Linux 
- edit the "/etc/xrdp/xrdp.ini" file to include the line:
    address=0.0.0.0
    right under #background=626x72 line. 0.0.0.0 is the local server address of xrdp
- Restart xrdp service
- allow xrdp port (probably 3389) through firewall
- We also need a VNC server. Install tightvncserver on Linux server machine. 
- run tightvncserver (no need to create a view-only password)
- "netstat -lvp | grep vnc" to check out the ports that tightvnc is listening on for 
    connections
- allow the vncserver port from the firewall: sudo ufw allow #
- allow the xrdp server
- Install xfce4 desktop environment an update to xfce, minimalistic faster and lightweight
    sudo apt-get install xfce4
- sudo apt-get install xfce4-terminal : way better than xterm
- sudo apt-get install gnome-icon-theme-full tango-icon-theme : installs icon sets
- Now we modify 2 files to make sure xrdp uses xfce4
    * echo xfce4-session >~/.xsession
    * secondly we modify startup file for xRDP located at /etc/xrdp/startwm.sh
        so it will start xfce4. Replace the last line with 
        startxfce4 
        (before it had something which started with a ., but no matter whatever it is, just 
        replace the last line)
    * restart xrdp service: sudo service xrdp restart
- Now you are ready to log into the computer from client using Remote Desktop (mstsc.exe). 
    Just supply the ipv4 or hostname of the VNC server.

III. *nix to / from *nix