Server test:
One the machine running the RDP server, run the following command in console (after enabling Remote login in Settings).
$ netstat -an --program | grep gnome-remote
This should show something like below:
tcp6 0 0 :::3389 :::* LISTEN 136861/gnome-remote
meaning that the gnome-remote-desktop-daemon is running and listening for connections on port 3389 (RDP port).
Client <—> Server connection test:
Next you can test the connection between the client and the machine running the RDP server using telnet as below:
If there are no connection issues, you should see the following:
$ telnet <server-ip> 3389
Trying <server-ip>...
Connected to <server-ip>.
Escape character is '^]'.
If there is connection issue (server firewall blocking connections), you’ll see the following:
$ telnet <server-ip> 3389
Trying <server-ip>...
telnet: Unable to connect to remote host: No route to host
FWIW, this is probably the default firewalld (enabled by default in Fedora) blocking connections to the server.