Applies To:
  • CitectSCADA 5.xx
Summary:

When a problem suddenly breaks the connection between applications communicating with CitectHMI/SCADA servers, whilst using the TCP/IP protocol, the license may not be freed.

This will occur with CitectHMI/SCADA to CitectHMI/SCADA communications when using the ini setting

[Lan]TCPIP=1

or CitectHMI/SCADA to CtAPI applications which always use TCP/IP.

The problem may take the form of a network outage, hardware failure, operating system failure or Software failure.

This is a Windows configuration issue. Microsoft Windows uses a "Keep Alive" packet to notify it that a network connection has been lost. By default Windows will send out a packet once every two hours. If there is no acknowledgement it retries a configurable number of times until it decides the network connection is no longer available and closes it. Since the default is two hours, licence counts may not be freed due to network problems for this length of time.

 

Solution:

WARNING - Modifying the registry of NT incorrectly may cause NT to behave unreliably or crash. As a result, it is possible you will be unable to change settings back to their original values. A complete reinstall of NT may be necessary to correct things. Therefore, take extra care when using the registry editor and when adding or changing parameters in the registry. A backup of the registry MUST be taken before attempting changes.

To decrease the time between "Keep Alive" packets being sent you must edit the Windows Registry and namely either add or edit the following key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\KeepAliveTime

Set the KeepAliveTime to something more suitable for CitectSCADA. A figure of 60000 will check after 1 minute.

Set the KeepAliveTime to something more suitable for CitectSCADA. A figure of 60000 will check after 1 minute.

For more Information see Citect Knowledge Base Article Q2533 - "Tuning Windows NT's TCP/IP suite to suit Citect"

 
Keywords:
licence license tcp tcp/ip network failure 

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