PORT-FORWARDING

Symptoms
By far the most common problem encountered by first-time users of VNC
is an inability to connect to a VNC Server that is behind a firewall
or a NAT router. This problem manifests itself with one of two error
messages:
Connection refused—This means that the IP address entered into the VNC
Viewer is valid, but that nothing is listening on the port you have
specified (or 5900 if you did not explicitly specify a port number).
Connection timed out—This means that nothing responded on the IP
address entered into the VNC Viewer, not even to reject the
connection.
Solution
The most common reason for seeing either of these error messages is
that you are entering the wrong IP address. The usual way of obtaining
the IP address of your VNC Server is to hover the mouse pointer over
the system tray icon:
However, it is common for computers not to be directly connected to
the Internet, but to be behind a firewall or a NAT router. In this
case, the IP address displayed by VNC Server is a private IP address
and is only valid if you are connecting from a computer behind the
same firewall/router. From any other location, the same IP address may
correspond to a different computer, or it may not correspond to any
computer at all.
To determine whether or not the IP address displayed by VNC Server is
the one you want, visit our VNC Server test page from the computer
running VNC Server. This page will tell you the IP address of the
computer from which you are browsing and also whether or not a VNC
Server is contactable at that address.
If the IP address displayed by that web page is not the same as the
one displayed by VNC Server when you hover the mouse pointer over the
system tray icon, then you are behind a NAT router, and the IP address
on the web page is the one you should use to connect from any computer
on the other side of that router (you might want to consider running a
free dynamic DNS client if this address changes frequently or you have
difficulty remembering it). If the web page indicates that it is not
able to connect to a VNC Server at that address, then you will have to
configure port forwarding on your router.
Note that links to the no-ip and portforwarding websites are included
for convenience only. These sites are not affiliated with RealVNC Ltd.
in any way.