Software Design
Spring 2007


RemoteObject lab exercise
-------------------------

1) Make sure Pyro is installed:

python
>>> import Pyro.core

1a) If not, become root and type 

yum install python-pyro

OR

wget http://wb/sd/code/Pyro-3.6.tar.gz
tar -xzf Pyro-3.6.tar.gz
rm Pyro-3.6.tar.gz           (just being tidy)
cd Pyro-3.6
su -                         (type the root password)
./setup.py install

For more information about Pyro, see http://pyro.sourceforge.net/

2) Download:

wget http://wb/sd/code/RemoteObject.py

This contains wrapper classes and some function that I wrote to
make Pyro easier to use.

wget http://wb/sd/code/SimpleRemoteObject.py

This contains an example that demonstrates the use of my classes.


2) Find a partner and decide who will run the client and who
   will run the server.

3a) If you are the server, disable your firewall, and then run
   
   python SimpleRemoteObject.py your_name_here

   The name that you provide has to be unique.  If someone else
   has already registered the same name on the name server,
   you will get an error.

3b) If you are the client, run

    python SimpleRemoteObject.py server_name_here 3 5

    The server_name_here you provide should be the name of
    your partner's server.

    The arguments 3 and 5 are converted to strings, and sent
    to the remote object where they are added and the sum
    returned an printed.

4) Read the code from SimpleRemoteObject.py and make sure
   you understand how it works:


class SimpleRemoteObject(RemoteObject):
    """this remote object exports the add method"""
    def add(self, x, y):
        print x, y
        return x + y

def server(name):
    """this is the code to start a SimpleRemoteObject server"""

    # instantiate the object
    simple = SimpleRemoteObject()

    # find the name server and
    # advertise this remote object
    ns = NameServer()
    simple.connect(ns, name)

    # wait for requests
    simple.requestLoop()

def client(name, x, y):
    """this is the code for a SimpleRemoteObject client"""

    # find the name server
    ns = NameServer()

    # instantiate a proxy for the remote object
    proxy = ns.get_proxy(name)

    # invoke a method on the proxy
    z = proxy.add(x, y)
    print z

def main(script, name='bob', x=None, y=None, *args):
    if x != None and y != None:
        # if the user provides arguments, run as a client
        x = int(x)
        y = int(y)
        client(name, x, y)
    else:
        # otherwise run as a server
        server(name)
        
if __name__ == '__main__':
    main(*sys.argv)