Parameters > Citect.ini File Parameters > LAN Parameters > [LAN]KeepAliveTime


Keep-alive packets are only sent when no data or acknowledgement packets have been received for a TCP connection within an interval.

The parameter controls how frequently TCP tries to verify that an idle connection is still intact by sending a KeepAlive packet. For example a connection between a CitectSCADA client and a server could be idle for a while if there are no requests and no tag value updates sent. The KeepAlive packet is a probe designed to elicit a response from the peer TCP. If the remote computer is still reachable and functioning, the remote computer acknowledges the KeepAlive transmission by returning an acknowledgement packet. If the peer has dropped the connection it will not respond with an acknowledgement segment.

In a TCP session established between two CitectSCADA processes, the KeepAlive packets are sent and acknowledged by both peers.

Lowering the value for the KeepAliveTime speeds up the time it takes to detect that a connection that has been dropped. However it also increases the network activity on idle connections. Conversely, increasing the value for this parameter will slow down the detection of a dropped connection, but decrease the activity on idle connections.

Allowable Values

Length of time in milliseconds

1 – 2147483647

Default Value: 3000

See Also