Firewalls can be a huge headache when you want computers
to work together. Hardware firewalls are less of a problem
because it's usually very clear whether or not there
is a hardware firewall between your computers. Software
firewalls ("personal firewalls", software
that runs on the same computer that you're trying to
protect) are more difficult because sometimes they cause
problems even when you think that they're turned off.
The Windows firewall is not a problem because KaVoom!
registers itself with the Windows firewall, allowing
other computers to connect.
In some cases (described below), turning on a
firewall solved the problem! (What happened was that
the firewall had been disabled incorrectly.)
Firewalls can prevent one computer from connecting to
another. When you're using KaVoom! what happens is that
you press the button to activate the secondary, the
screen turns black, and nothing else happens. A minute
later, a message box is displayed with an error such
could not be contacted. Failed to connect to (nil) IP
This means that there is firewall software preventing
KaVoom! from accessing the network.
One customer reported that Norton Internet Security
did this even after it was disabled. He uninstalled
the firewall software entirely and then KaVoom! worked
One customer reported that Zone Alarm continued
to block network connections even if he did not start
it (e.g., he deleted the icon from the Start Up menu).
But if he started Zone Alarm and the stopped it, then
KaVoom! worked fine. The reason for this behaviour is
that Zone Alarm also has a service running in the background
(the True Vector engine) which starts as soon as the
computer starts, even if the Zone Alarm icon is deleted.
A customer reported that Computer Associates E-trust
software behaved in a similar way; it blocked network
connections even though it was disabled in msconfig.
He re-enabled the firewall software and the firewall
then permitted the network connection to succeed.
It is sometimes helpful to use the telnet utility that
comes with Windows to test whether or not a firewall
is preventing a connection to your computer.
The telnet test is helpful because it helps confirm
that a software firewall is the problem, even though
you might think that the firewall has been disabled.
Step 1. Go to the computer that you are
trying to connect to. For KaVoom! KVM, this is one of
the secondary computers.
Step 2. Start a command prompt by selecting
Run from the Start menu and typing "cmd" into
the box, then press OK.
Step 3. At the command prompt, type "telnet
localhost NNNN", where NNNN is the port number
that the application uses, usually 5222 for KaVoom!
KVM, 5225 for KaVoom! KM, or 5250 for Desktop One.
You should see a message such as "KaVoom! KM is
running and the port is open". If not, the software
is not running. (On versions of KaVoom! KVM earlier
than 3.59, you won't see this message, but you'll see
some scrambled data that indicates that the port is
open. Similarly with versions of KaVoom! KM earlier
Step 4. On the same computer, type "telnet
x.x.x.x NNNN", where x.x.x.x is the computer's
IP address, and NNNN is the application's port number.
You should see the same message as above. (Note: Different
firewalls behave differently. The ZoneAlarm firewall
will prevent the message from being displayed, but the
Windows firewall will not. So just because you see the
message as expected, a firewall might still be causing
Step 5. Go to the computer that you're
trying to connect from. Open a command prompt as above
and type "telnet x.x.x.x NNNN", as described
above. You should see the same message as above. If
not, it means that you have a software firewall on this
computer that is preventing telnet from accessing the
If telnet is able to connect from one computer to the
other, then KaVoom! should be able to connect too.