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

[Arne Vajhøj]

On 6/21/2023 4:45 PM, Jan-Erik Söderholm wrote:
> When doing a *read* from a terminal device using QIOW, one
> can use IO$M_TIMED and supply a timeout value in P3. That
> works perfectly and we use that a lot.
> 
> 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.
> 
> As far as I can see, QIO/QIOW does not support a timeout value
> when used for writing, is that correct?

Yes.

https://vmssoftware.com/docs/VSI_IO_REF.pdf

Table 5.6 lists IO$M_TIMED for IO$_READ* while table 5.8
does not list it for IO$_WRITE*.

> I was hoping that one could add a timeout value just as in the
> read case, but it doesn't look so. So I do not see how to get
> out of the hanging call to QIOW. Maybe using QIO, and doing
> some extra coding to check the I/O, I guess.
> 
> So, is there a way to get out of this state, still using QIOW?

Totally untested idea:

SYS$SETIMR with an AST routine that calls SYS$CANCEL

Arne