It can be frustrating when you try to start xwindow application using Xming XServer on Windows XP/7/Vista but encountering connection refused error. Here is an example of the error:
[oracle@oel5 /]$ dbca Xlib: connection to "192.168.0.100:0.0" refused by server Xlib: No protocol specified
Here is a quick tip to fix this issue:
In Windows, look for the shortcut to start Xming. Right click your mouse to go to properties.
add -ac to your XMing shortcut:
"C:\Program Files (x86)\Xming\Xming.exe" :0 -clipboard -multiwindow -ac
The -ac parameter allows everyone to connect.
restart Xming and try again.