[ale] question regarding how to see if a computer is listening on a port or rejecting connections..

[David Ritchie]

ALE folk,
    I suspect that this is something that someone else has already
solved, so I thought I would pose the question to the ALE hive mind...

I have a printer with a network interface. it is sporadically going on
and off line within the TCP stack. For example, if you were to do a

        telnet <IP address> 9100

it would either connect, or refuse the connection. It typically stays
down once it crashes.

Pings always respond, but the TCP stack crashes and the only
consistent way to get this
to reset is to turn the printer off for 15 minutes (to allow the power
to full go down on the internal network card). It will resume
operation for a while
until it hangs again. We have tried updating the cards, etc and are
working (slowly) with the vendor to correct the problem.

What I am looking for something that I can use to determine this kind
of connection is failing. Looking for suggestions.. perhap nc could do
this? (not
really experienced with nc, but that comes to mind)...

Best regards,
Dave Ritchie