[root@orcltest ~]# export DISPLAY=localhost:1
[root@orcltest ~]# xhost
xhost: unable to open display "localhost:1"
[root@orcltest ~]#
 
[root@orcltest ~]# export DISPLAY=127.0.0.1:1
[root@orcltest ~]# xhost
xhost: unable to open display "127.0.0.1:1"
[root@orcltest ~]# xhost +
xhost: unable to open display "127.0.0.1:1"
[root@orcltest ~]# xhost + 192.51.3.12
xhost: unable to open display "192.51.3.12:1"

   [root@orcltest ~]# vim /root/.vnc/orcltest:1.log
 
 
   Xvnc TigerVNC 1.1.0 - built May 11 2016 13:01:55
   Copyright (C) 1999-2011 TigerVNC Team and many others (see README.txt)
   See http://www.tigervnc.org for information on TigerVNC.
   Underlying X server release 11704000, The X.Org Foundation
 
 
   Tue Mar 14 03:23:26 2017
   vncext:  VNC extension running!
   vncext:  Listening for VNC connections on all interface(s), port 5901
   vncext:  created VNC server for screen 0
   GNOME_KEYRING_SOCKET=/tmp/keyring-jRupIx/socket
   SSH_AUTH_SOCK=/tmp/keyring-jRupIx/socket.ssh
   GNOME_KEYRING_PID=7358
   Cleaned 21 files 7 still live
   Failed to play sound: Not available
 
   (polkit-gnome-authentication-agent-1:7380): GLib-GObject-WARNING **: cannot register existing type `_PolkitError'
 
   (polkit-gnome-authentication-agent-1:7380): GLib-CRITICAL **: g_once_init_leave: assertion `initialization_value != 0' failed
 
   ** (gnome-user-share:7381): WARNING **: gnome-user-share cannot be started as root for security reasons.
   Initializing nautilus-gdu extension
 
   ** (gnome-panel:7372): WARNING **: panel-applet-frame.c:1288: failed to load applet OAFIID:GnoteApplet:
   (null)
 
   ** (gnome-panel:7372): WARNING **: panel-applet-frame.c:1288: failed to load applet OAFIID:GNOME_FastUserSwitchApplet:
   (null)

   [root@orcltest ~]# xdpyinfo
   -bash: xdpyinfo: command not found
   [root@orcltest ~]# yum install -y xdpyinfo
   Loaded plugins: refresh-packagekit, security
   Setting up Install Process
   Resolving Dependencies
   --> Running transaction check
   ---> Package xorg-x11-utils.x86_64 0:7.5-14.el6 will be installed
   --> Processing Dependency: libdmx.so.1()(64bit) for package: xorg-x11-utils-7.5-14.el6.x86_64
   --> Processing Dependency: libXxf86dga.so.1()(64bit) for package: xorg-x11-utils-7.5-14.el6.x86_64
   --> Running transaction check
   ---> Package libXxf86dga.x86_64 0:1.1.4-2.1.el6 will be installed
   ---> Package libdmx.x86_64 0:1.1.3-3.el6 will be installed
   --> Finished Dependency Resolution
 
   Dependencies Resolved
 
   ===============================================================================================================================================================================================================================================================================
   Package                Arch               Version                 Repository             Size
   ===============================================================================================================================================================================================================================================================================
   Installing:
   xorg-x11-utils              x86_64              7.5-14.el6                base              101 k
   Installing for dependencies:
   libXxf86dga               x86_64              1.1.4-2.1.el6               base               18 k
   libdmx                x86_64              1.1.3-3.el6                base               15 k
 
   Transaction Summary
   ===============================================================================================================================================================================================================================================================================
   Install  3 Package(s)
 
   Total download size: 133 k
   Installed size: 270 k
   Downloading Packages:
   (1/3): libXxf86dga-1.1.4-2.1.el6.x86_64.rpm                                                    | 18 kB  00:00 
   (2/3): libdmx-1.1.3-3.el6.x86_64.rpm                                                     | 15 kB  00:00 
   (3/3): xorg-x11-utils-7.5-14.el6.x86_64.rpm                                                    | 101 kB  00:00 
   -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
   Total                                                           252 kB/s | 133 kB  00:00 
   Running rpm_check_debug
   Running Transaction Test
   Transaction Test Succeeded
   Running Transaction
   Installing : libXxf86dga-1.1.4-2.1.el6.x86_64                                                       1/3
   Installing : libdmx-1.1.3-3.el6.x86_64                                                         2/3
   Installing : xorg-x11-utils-7.5-14.el6.x86_64                                                       3/3
   Verifying : libdmx-1.1.3-3.el6.x86_64                                                         1/3
   Verifying : xorg-x11-utils-7.5-14.el6.x86_64                                                       2/3
   Verifying : libXxf86dga-1.1.4-2.1.el6.x86_64                                                       3/3
 
   Installed:
   xorg-x11-utils.x86_64 0:7.5-14.el6                                                           
 
   Dependency Installed:
   libXxf86dga.x86_64 0:1.1.4-2.1.el6                          libdmx.x86_64 0:1.1.3-3.el6                          
 
   Complete!
   [root@orcltest ~]#

   [root@orcltest ~]# xdpyinfo
   xdpyinfo: unable to open display "localhost:1".
   [root@orcltest ~]# xhost + 192.51.3.12
   Xhost: unable to open display "localhost:1"
   [root@orcltest ~]# export DISPLAY=:1.0 
   [root@orcltest ~]# xhost +
   access control disabled, clients can connect from any host
   [root@orcltest ~]#