"Can't open display" occurs in tigervnc after upgrade to RHEL6.8

Issue

• "Can't open display" occurs in tigervnc after upgrade tigervnc-server to tigervnc-server-1.1.0-18.el6 (RHEL 6.8)
• After login to remote desktop via VNCviewer, X application can display locally, but cannot forward via TCP. Eg, after login to remote desktop via vncviewer, open a terminal inside vncviewer, and try:

  $ echo $DISPLAY
  :2.0
  $ xclock <---- Succeed.

  $ ip a | grep inet | grep global
  192.168.122.46

  $ xhost +
  $ export DISPLAY=192.168.122.46:2.0
  $ xclock
  Error: Can't open display: 192.168.122.46:2.0  <---- Fail