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webMathematica User Guide 27Xlib:Client is not authorized to connect to Serverxset:unable to open display ":0.0"Xlib:connection to ":0.0" refused by serverXlib:Client is not authorized to connect to ServerXMathematica:can't open display:0.0,exiting...bash$One way to avoid this problem is to allow all connections from the local machine.[root]# xhost +localhostlocalhost being added to access control list[root]# su tomcatbash$ mathematicabash$This is not a good technique since there is a potential for security problems. These are probablylimited since it is only connections from the same machine that are allowed. Another problem isthat every time the front end is used, a window will be drawn on the screen, which may beannoying to a user of the system.A more satisfactory alternative is to run a virtual X server, such as Xvnc.XvfbXvfb is a virtual frame buffer server described at http://www.xfree86.org/4.3.0/Xvfb.1.html. Itcan be used as an alternative to Xvnc, but typically we have found Xvnc to be easier to use andprovide more functionality.For Linux, you can download an RPM archive from http://www.redhat.com. After installation,you can launch it as follows (you will probably run this as root).su tomcat -c "/usr/X11R6/bin/Xvfb :1 -fpunix/:7100,/usr/local/Wolfram/Mathematica/4.2/SystemFiles/Fonts/Type1,/usr/local/Wolfram/Mathematica/4.2/SystemFiles/Fonts/BDF -screen 0800x600x24 " &This command launches Xvfb referencing a font server on port 7100 and adding directories thatcontain the Mathematica fonts. Note that if you install Mathematica in some alternative location,you should modify these directories. Under some Mathematica installations the location ofMathematica fonts is added to the font server configuration; in this case the Mathematica fontsdo not need to be referenced when Xvfb is launched. Xvfb could then be launched as shownhere.su tomcat -c "/usr/X11R6/bin/Xvfb :1 -fp unix/:7100" &