Every time i try to connect to VNC i get an error message

ConnectedException in thread "main" java.lang.NullPointerException
    at edu.unh.iol.dlc.Framebuffer.resetPF(Framebuffer.java:84)
    at edu.unh.iol.dlc.VNCThread.setPixelFormat(VNCThread.java:147)
    at edu.unh.iol.dlc.ConnectionController.setPixelFormat(ConnectionController.java:117)
    at test_run_01.main(test_run_01.java:24)

Can anyone please help , why this is happening.
I am using Tiger VNC , running on RHEL 6

code:

public static void main(String[] args){
Socket s = new Socket("192.168.1.17", 5900);
s.setSoTimeout(1000);
s.setKeepAlive(true);
ConnectionController cc = new ConnectionController(s);
cc.openConnection(0);
cc.setPixelFormat(0, "Truecolor", 32, 0);
cc.start(0);
Thread.sleep(2000);
VNCScreen vnc = new VNCScreen();
cc.closeConnection()