sending data to another process's input stream?

[Steven D. Majewski]

On Thu, 20 May 1999, Joe Strout wrote:

> In article <14148.28634.948802.403019 at amarok.cnri.reston.va.us>, Andrew
> M. Kuchling <akuchlin at cnri.reston.va.us> wrote:
> 
> >         The most frequent solution would be to use sockets, whether
> > Unix or TCP/IP. 
> 
> Ugh.  I was afraid you'd say that.  But what's the difference between
> Unix and TCP/IP sockets?  I poked around the Python library reference,
> and found only "sockets" (no distinction).
> 

Unix sockets are just "named pipes" . Open with AF_UNIX instead of
AF_INET in the socket call. You bind to a name ( which gets entered
into the directory namespace just like a file ) instead of a well 
known port number. ( This isn't in the Python reference because it's
specific to the hosts socket implementation. There's not AF_UNIX mode
on MacPython for example (not that it couldn't be emulated).)

You can also use AF_INET sockets and the 'loopback' address when you're
client & server are one the same host, but Unix sockets should be 
more effecient. 

> >  So, you could write a Python program that would be a long-lived
> > server and accepted connections over a Unix or TCP/IP socket; CGIs
> > would then talk to the server.  (This is how Zope works, for example.)
> > Your server could then just act as a front-end for a single
> > long-running instance of the C++ program, sending output to the
> > program's standard input.
> 
> Hmm... but that doesn't help, does it?  Before, my question was how to
> get the short-lived CGIs talking to my long-lived C++ program.  With
> your suggestion, the question is how to get the long-lived Python
> server to talk to the long-lived C++ program.  It's the same question,
> is it not?


I think by "Your server could..." he meant the short-lived CGI which
gets run from your HTTP server. ( Which, if it is run from inetd 
is also 'short-lived', which is why it's not usually run from inetd.)

Zope works very much like what you want, except that Zope serves 
persistent Python objects, and you want to serve C++ objects. 
( Unless you want to wrap you C++ objects as Python objects and 
  do it all in Python. ) 

> Put another way, how would I implement this part:
> 
> > Your server could then just act as a front-end for a single
> > long-running instance of the C++ program
> 
> ?  Are sockets the way to go, or is there anything easier?
 
sockets are probably the easiest. 

---|  Steven D. Majewski   (804-982-0831)  <sdm7g at Virginia.EDU>  |---
---|  Department of Molecular Physiology and Biological Physics  |---
---|  University of Virginia             Health Sciences Center  |---
---|  P.O. Box 10011            Charlottesville, VA  22906-0011  |---

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