Tigervnc-server does not refresh screen automatically on client side sometimes

[ashutosh shukla]

want to use tigervnc-server for sharing existing desktop via x0vncserver

 it works but sometimes on the client side screen do not refresh automatically 

 it refreshes when clicked by mouse .. 

using polling at 20 value .. 

can somebody give any idea .. so that do not have to use mouse at  the client side 

and vnc refreshes screen automatically .