From: schristensen@daimi.aau.dk (Soren Christensen)
To: designCPN@daimi.aau.dk
Date: Fri, 19 Jul 1996 13:14:04 +0200
Subject: Re: Possibility to communicate with a running Unix-process?

[[ Below, Soren has made a communication example. You need to do the following
   in order to build the sub_process executable. Execute cpn.ML (the SML 
   compiler) directly from a shell script. At the "-" prompt type
     use "sub_process.sml";
   and the return key. After a few minutes, kill the SML compiler manually
   (as it will not terminate after it has completed saving the sub_process
   executable). The executable file sub_process has now been generated, and 
   now you are ready to read Soren's example.

   Additionally to Soren's example, I've included an example where the 
   external executable communicated with is a Tcl/Tk script. In the global
   declaration node, change the execute file path to point to the Tcl/Tk 
   script sub_process.tcl.

   (If you do not see any graphical feedback when simulating the model,
   please start manually a cpnmld daemon with a new port number. I do
   not know why this is necessary, but at least it works for me.)

   /Kjeld H. Mortensen (moderator)
]]

If you assume some limitations it is not that hard to do.

I have created a small example which assumes the following:
1) the external process can be started as a sub-process.
2) the communication will be done using std_in/std_out of the sub-process.

In
  http://www.daimi.aau.dk/designCPN/email/p/models/post960720a.tar.Z
you'll find a model (process, process.DB) and the SML source file
sub_process.sml to build an executable (sub_process). When sub_process
is started via the process example in Design/CPN the sub-process will create 
and write to a log file called /tmp/log_prc.log. (During simulation, read the
log file with "tail -f" in a shell window.)

In this way it is possible for the simulation to controle an external
process, the other way is much harder!

Remember to set the path to the sub_process executable in the global 
declaration node before you try the example.

Soren


---------------------------------------------------------------------
| Soren Christensen, Computer Science Department, Aarhus University |
| Ny Munkegade 116, DK-8000 Aarhus C, DENMARK                       |
| email: schristensen@daimi.aau.dk | phone: +45 89 42 32 65         |
| telefax: +45 89 42 32 55         | phone at home: +45 86 93 63 26 |
| WWW URL: <http://www.daimi.aau.dk/~sorenchr>                      |
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>I am working on my master thesis with Design/CPN 3.01. The background
>of the thesis is a simulation of the PROFIBUS system.
>
>To present some results to the user outside Design/CPN, while
>the petri net of the bus simulation is still running, i need
>to trigger an external process. This process then reads some
>data from a file and updates a Tcl/Tk - application.
>
>How can i manage this trigger effect?
>
>Busy waiting can not be used due to the slow machine, i am
>currently working on. The simulator eats up all the processor time.
>
>Has anyone solved a similar problem?
---
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