Why can’t I access my VNC Server even though I’m entering the right password?

June 4, 2009

There are a couple of possible causes of problems authenticating yourself to the VNC Server. The most basic of these is that you have not configured a VNC Authentication password – VNC Server won’t let you connect without supplying a password unless the server is explicitly configured to use No Authentication.

If you have previously used VNC Free Edition, and have upgraded to a secure version, you may find that VNC Server rejects your password if it is longer than eight characters. You should find that you can connect successfully if you only enter the first eight characters of your password when prompted for it by VNC Viewer. You can enable your full length password by re-setting it, using the appropriate configuration tool for your platform.

Under Windows, VNC Server can only map keyboard input to the correct characters if all programs are using the same keyboard layout as the operating system. This can cause authentication problems if affected characters appear in the server’s password.

Why can I access my VNC Server even though I’m entering the wrong password?

The short answer is: You can’t! However, when the classic VNC Authentication scheme is used to authentication the user, only the first eight characters of the user’s password are checked. This means that the passwords “01234567hello” and “01234567world”, for example, would be regarded by VNC Server as identical.

This is a limitation only when using VNC Free Edition or older VNC software. If both the Viewer and Server support encryption then the full password will be checked, even if encryption is not actually enabled.


VNC Viewer Free Edition 4.1 for Windows…