[Info-vax] Timeout in a write using QUIW.

[Simon Clubley]

On 2023-06-21, Jan-Erik Söderholm <jan-erik.soderholm at telia.com> wrote:
>
> Now, we are having issues with an application when *writing*
> to a terminal (TNA) device using QUIW that points to a small
> label printer. If the printer is offline or not accessable on
> the network, the application just hangs.
>

[snip]

>
> These are new printers where they decided to use Wifi
> instead of wired connection. We do not see these issues
> on our older label printers which are all hard wired...
>
> I will of course again suggest that they do take the cost to
> ask for wired network connections instead of using Wifi...
>
> I also fixed a COM file that pings these 7 printers once each
> 10 seconds, and it clearly shows that the connections comes
> and goes more or less all the time. And when that happens to
> be the same time as they try to print a label, it just hangs...
>

Others have given you some excellent workarounds, but I am more
interested in _why_ you have the problem in the first place.

First off, it's not fully clear, but are these label printers
directly on the network, with their own IP address, instead of
via a terminal server ? I am assuming they are directly on the
network for the rest of this post.

It sounds like you have a permanent TCP/IP connection to the
printers via reverse telnet. In that case, do you have keepalive
packets from VMS enabled on the connection ?

If you do, but the keepalive interval is 75 seconds or greater,
try reducing it to 30 seconds in case the printers are going into
some wireless low-power mode after a short period of time of network
inactivity.

(30 seconds is what I tell ssh to use for keepalive packets when
I use WAN connections, and it seems like a reasonable value to me.)

If that works, look to see if the printers have some low-power settings
that can be adjusted or disabled.

The keepalives should end up with the telnet connection being dropped
by VMS on failure, so that you can reconnect.

Is there anyway you can do the telnet connection on demand and then
tear it down again immediately afterwards, instead of keeping it open
all the time, even when you are not printing labels ?

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.