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

[Jan-Erik Söderholm]

Den 2023-06-22 kl. 01:16, skrev Dave Froble:
> On 6/21/2023 5:17 PM, Arne Vajhøj wrote:
>> 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
>>
>>
> 
> Damn, Arne beat me to it.  However while I use that for reads, I've never 
> used it for a write.  Don't know what would happen.  Best to test.
> 

But for reads, it is easier to just add the timeout to the QIOW
call directly. No added code.

And thanks for you input!

Jan-Erik.