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Customer Support - Firewalls

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 as: could not be contacted. Failed to connect to (nil) IP number 1:10061

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 fine.

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.

The Telnet Test

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 than 2.03.)

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 a problem.)

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 other computer.

If telnet is able to connect from one computer to the other, then KaVoom! should be able to connect too.

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