lock access to serial port

[kkadrese at gmail.com]

not the goal setup but the way I tried it out - a webpage to send an
sms to mobile phone. This is an php what calls a python script. A
python script opens serial device, checks for gsm network, sends a
message - on all the way I try to make sure that appropriate answers
are received from the gsm device so that I know that all is going well
(and if not - cancel it with error message).

Testing it with sending an sms from two open webpages, I normally got
that one message was sent and for the other I received "try once more,
happened that and that". But I got also an inadmissible situation -
the received sms contained also unwanted text. As far as I can realize
how to deal with it is not allowing writing to the device for two
processes simultaneously.


Andra


On 19 Marts, 11:00, taco <trala... at joepie.nl> wrote:
> kkadr... at gmail.com wrote:
> > hello group,
>
> > how to get ttyS0 serial port for exclusive access? I have a python
> > script that uses this device with AT commands. I need that two
> > instances can call simultaneosuly this python script but only one of
> > them gets the device. I tried fcntl.flock, it was just ignored, put
> > writtable file LCK..ttyS0 in /var/lock, tried ioctl (but I may not
> > know what are appropriate arguments), googled half a day for various
> > phrases, error messages etc....without success.
>
> > please help,
>
> > Andra
>
> not sure if I understand you well, but how about a server application which
> accepts 2 clients which can send messages which are output on the serial
> device? The serial device access protected with a mutex while receiving
> messages done in 2 threads or something.
> taco