Python Cookbook

Implementing a CORBA Client and Server

Credit: Duncan Grisby

Problem

You need to implement a CORBA server and client to distribute a processing task, such as the all-important network-centralized, fortune-cookie distribution.

Solution

CORBA is a mature object-oriented RPC protocol, and several CORBA ORBs offer excellent Python support. This recipe requires multiple files. Here is the interface definition file, fortune.idl:

module Fortune {
  interface CookieServer {
    string get_cookie(  );
  };
};

The server script is a simple Python program:

import sys, os
import CORBA, Fortune, Fortune_ _POA

FORTUNE_PATH = "/usr/games/fortune"

class CookieServer_i(Fortune_ _POA.CookieServer):
    def get_cookie(self):
        pipe   = os.popen(FORTUNE_PATH)
        cookie = pipe.read(  )
        if pipe.close(  ):
            # An error occurred with the pipe
            cookie = "Oh dear, couldn't get a fortune\n"
        return cookie

orb = CORBA.ORB_init(sys.argv)
poa = orb.resolve_initial_references("RootPOA")

servant = CookieServer_i(  )
poa.activate_object(servant)

print orb.object_to_string(servant._this(  ))

poa._get_the_POAManager().activate(  )
orb.run(  )

And here’s a demonstration of the client code, using the Python interactive command line:

>>> import CORBA, Fortune
>>> orb = CORBA.ORB_init(  )
>>> o = orb.string_to_object(
...   "corbaloc::host.example.com/fortune")
>>> o = o._narrow(Fortune.CookieServer)
>>> print o.get_cookie(  )

Discussion

CORBA has a reputation for being hard to use, but it is really very easy, especially if you use Python. This example shows ...