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Configuring
the Windows Firewall
The Microsoft Internet
Connection Firewall allows users to prevent unauthorized applications from
accessing your computer using communication ports into your computer.
In order for ClockWatch to communicate with timeservers you must allow
communication with the specified servers using the ports specified.
Starting with Windows XP Service Pack 2 Microsoft offered an enhanced firewall that
restricts communication to external sites. These restrictions may
interfere with the normal operation of time synchronization products. You then
must explicitly allow communication through the ports used in communicating with
external timeservers.
This describes how to configure the firewall to allow time protocol
communication messages such as NTP and NIST between external timeservers and ClockWatch.
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You must allow exceptions if your firewall is on
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Open the firewall control panel.
To open Windows Firewall, click
Start, click Control Panel, and then double-click
Windows Firewall.
Confirm that exceptions are allowed, so the settings are set like this |
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Note that we have already allowed the ClockWatch
Application and Service. In many ways this is a simpler way to allow the
ClockWatch timeserver to work. |
On the Exception tab click on 'Add Port'
An alternative method
would be click on the 'Add Program' to select the ClockWatch application
and ClockWatch Service.
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In this example we are adding a setting to allow NTP over port 123 using the UDP
communication protocol.
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Name: Identify the port with the time protocol in use
(NTP, SNTP, NIST, Daytime or Time)
Port number, is based on the protocol used:
- NTP and SNTP use port 123 on time servers.
- NIST and Daytime use port 13
- Time uses port 37
Communication protocol, is also dictated by the time
protocol in use:
- NTP and SNTP use User Datagram Protocol (UDP) for
communication.
- NIST and Daytime use TCP
- Time uses either TCP or UDP
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NTP time protocol communication is now permitted |
Press OK, and NTP should be now be allowed through the firewall. |
ClockWatch Firewall Page
ClockWatch Main Page
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