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 Q: I have a timer expiration/network disconnected error message. What does it mean?
\DosDevices\COM7: The Keep-Alive timer expired.
The network connection has been disconnected.
A: This error means that the NativeCOM driver has lost an active connection with an Systech Device Server (RCS, POS, NPS, NDS or INS/ixNS series) unit.

Whenever a port (e.g., COM7) is open, the NativeCOM driver keeps a TCP connection open to the Systech Device Server unit and periodically sends a "Keep Alive" message to ensure that the connection is still working. If it does not get a response from the unit within a prescribed amount of time, it assumes the connection has died for some reason, closes it, and begins trying to re-establish it. All of this is largely transparent to the application. (One thing an application might get is a message saying the modem signals were lost on the port.)

Some possible causes for the loss of the "Keep Alive" are:
  • The Systech Device Server is disconnected from the netowrk, powered off, or reset.
  • The Systech Device Server is remotely located and the WAN connection is severed.
  • The PC with NativeCOM is removed from the network.
  • The network is disrupted (e.g., a hub stops working)

Unless this is happening frequently or is causing your applications problems, you can probably ignore it. If you have a remote connection that is slow (e.g., dial up) or a system that is very busy, you can increase the timeouts on the "Keep Alive" to prevent the connections from being unnecessarily lost, but this is unusual.
    Answer Last Updated: September 25, 2008
 

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