Programming with Reflection

image\rwnprg32.gif TelnetKeepAlive property



object.TelnetKeepAlive = Value

Data type




Returns (first syntax line) or specifies (second syntax line) whether Reflection periodically polls the host to determine if Telnet connections remain active during intervals when you are not sending data to the host. Normally, Reflection becomes aware of Telnet communication problems only after a significant delay, or when it attempts to send data to the host. Because of this, you can lose your connection to the host and not be immediately aware of it. This can cause problems if you enter a large amount of data on one screen, or if you keep your connection open during periods of inactivity.

To become aware of connection problems as they occur, you can configure Reflection to send Keep Alive packets.


The default value is rcKeepAliveNone.

rcKeepAliveNone Reflection does not send any keep alive packets to the host.

rcKeepAliveNOP Reflection periodically sends a No Operation (NOP) command to the host. The gateway and host are not required to respond to these commands, but the TCP/IP stack can detect if there was a problem delivering the packet. Use KeepAliveTimeout to control the interval between requests.

rcKeepAliveSystem The TCP/IP stack keeps track of the host connection. This value requires less system resources than rcKeepAliveTimingMark or rcKeepAliveNOP, but most TCP/IP stacks send Keep Alive packets infrequently.

rcKeepAliveTimingMark Reflection periodically sends a Timing Mark Command to the host to determine if the connection is still active. The gateway or host should respond to these commands. If Reflection does not receive a response or there is an error sending the packet, it will shut down the connection. Use KeepAliveTimeout to control the interval between requests. The TelnetKeepAliveAverage property returns the average amount of time Reflection has waited for a response to a Timing Mark Command.



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