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Re: Problems with up and down going connections

bryan bryan@conserver.com
Sun, 28 Apr 2002 00:05:07 -0700 (PDT)

Quoting Marcel Heemst van <MHEE@fuji-ef.nl>:
> But...
> When the terminal server is going down and the conserver was already
> started, console -u NEVER detect the connections down.
> When the terminal server is going up and the conserver was  already
> started,
> console -u NEVER detect the connection up.

This is true.  The first issue is that the conserver host isn't seeing any 
problem with the TCP connection to the terminal server.  If the TCP session 
goes down, conserver will notice the problem and bring the consoles to the down 
state (and try and reconnect, actually).  Usually it only happens when a 
terminal server crashes or gets power cycled (it doesn't have a chance to abort 
all the TCP connections).  There's really not much that can be done here, since 
conserver is relying on the underlying TCP stack to do it's job - most 
applications would have this same problem (if you were to connect to one of 
those consoles and try and interact with it, conserver would immediately get a 
TCP failure and bring it down - after trying to reconnect).  The idea of having 
conserver "ping" the terminal servers to make sure they're up doesn't really 
appeal to me (right at this moment), but maybe someone would have a good idea 
of how to do this - that way terminal servers that drop off the net (for 
whatever reason) would be detected sooner.  But, ideally, this is a small edge 
case and not the norm (rebooting a terminal server *should* trigger TCP session 
closures - at least, if the terminal server was doing "the right thing").

As for the second problem (conserver already running and a terminal server is 
booted), there are a couple of options.  The first is to use another app to 
watch your terminal servers and send conserver a SIGUSR1 whenever it wants 
conserver to try and reconnect to all the consoles marked as down.  Another 
option is to use the -o/-O options and have conserver automatically try and 
reconnect all the downed consoles.  Between those two methods, I hope something 
works for you.

> This problem can we solve with:
> Start a console session to this port and use the ^Eco string.
> But we want to have a functionality to redetect the connection state
> automaticly, because we have an another application which is detect
> the
> connection state and generate alarm then the connection is down.

Hopefully one of those methods above works in this case.