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Description of problem:
- VNC will not start on port 5901 because of a socket conflict

Version-Release number of selected component (if applicable):
- tigervnc-server-1.3.1-3.el7
- xorg-x11-server-Xorg-1.17.2-10.el7

How reproducible:
- clean installation of RHEL 7.2 "server with GUI"
- clean installation of tigervnc-server
- configure unit file for vncserver@:1.service for user
- set vncpassword for user
- enable and start daemon
- daemon fails as follows:
Warning:<hostname>:1 is taken because of /tmp/.X11-unix/X1
Remove this file if there is no X server <hostname>:1
A VNC server is already running as :1


Actual results:
- vncserver will not start on this port

Expected results:
- vncserver starts on port 5901

Additional info:

Find display number:

if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
    $displayNumber = $1;
    shift(@ARGV);
    if (!&CheckDisplayNumber($displayNumber)) {
        die "A VNC server is already running as :$displayNumber\n";
    }
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
    &Usage();
} else {
    $displayNumber = &GetDisplayNumber();
}

$vncPort = 5900 + $displayNumber;

Looks like its just dying instead of moving to the next display

Fixed in tigervnc-1.3.1-6.el7.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-2237.html