How to clean up socket connection to printer
ulrich.eckhardt at dominolaser.com
Tue Jul 9 16:05:08 CEST 2013
Am 09.07.2013 11:39, schrieb loial:
> I have a socket application that is connecting to a HP printer via port 9100.
> Occassionally I get a "Connection reset by peer" error which I am
> trapping and exiting the script with an error message.
Strange. Why does the remote terminate the connection?
> That works Ok, the issue I have is that the next time I run the
> script I get "Connection refused" from the printer, which
> suggests that the printer still thinks the port is is busy,
> though nothing is printing. I suspect that in some way my socket
> connection has not been closed correctly?
I'm assuming you are using TCP. Getting a "connection refused" rather
means that there is no server process that is listening on that port. It
sounds a bit as if the printer was kind-of rebooting itself, which first
resets the existing connection and then, after a rebooting, opens the
port again for connections.
1. Does the printer accept connections again after some time?
2. Does the printer accept connections if you close and re-open the
3. Is there actually a limit to the number of concurrent connections? In
other words, what happens when you try to create a second connection
without closing the first?
> When I get the "Connection rest by peer" error, I attempt to close
> the port as follows :
This is useless, the connection is already closed at that point.
Your description suggests that it is a remote problem. I still wouldn't
rule out that it is somehow caused by your code though, but without
seeing that, it's impossible to tell.
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