PYRO - Example

## 8. Example

In this chapter you'll find a short but complete example that shows how Pyro must be used and how it works. However, much more interesting examples can be found in the `examples` directory. For the real impatient people, I recommend the "quickstart" example, because you'll see that you can eliminate very much of the (already little!) extra work you have to do to make a Pyro application.

For the really impatient, first two minimalist Pyro examples.

### Minimalist's Pyro - not using a Name Server

Server:

      import Pyro.core

      class JokeGen(Pyro.core.ObjBase):
              def __init__(self):
                      Pyro.core.ObjBase.__init__(self)
              def joke(self, name):
                      return "Sorry "+name+", I don't know any jokes."

      def main():
          Pyro.core.initServer()
          daemon=Pyro.core.Daemon()
          uri=daemon.connect(JokeGen(),"jokegen")

          print "The daemon runs on port:",daemon.port
          print "The object's uri is:",uri

          daemon.requestLoop()

      if __name__=="__main__":
          main()

Client:

      import Pyro.core

      # you have to change the URI below to match your own host/port.
      jokes = Pyro.core.getProxyForURI("PYROLOC://localhost:7766/jokegen")

      print jokes.joke("Irmen")

### Minimalist's Pyro - using a Name Server

Server:

      import Pyro.core
      import Pyro.naming

      class JokeGen(Pyro.core.ObjBase):
              def __init__(self):
                      Pyro.core.ObjBase.__init__(self)
              def joke(self, name):
                      return "Sorry "+name+", I don't know any jokes."

      def main():
          Pyro.core.initServer()
          ns=Pyro.naming.NameServerLocator().getNS()
          daemon=Pyro.core.Daemon()
          daemon.useNameServer(ns)
          uri=daemon.connect(JokeGen(),"jokegen")
          daemon.requestLoop()

      if __name__=="__main__":
          main()

Client:

      import Pyro.core

      # finds object automatically if you're running the Name Server.
      jokes = Pyro.core.getProxyForURI("PYRONAME://jokegen")

      print jokes.joke("Irmen")

### There we go with the complete example:

1. Write a module 'testmod.py' containing a class 'testclass', which will be accessed remotely.

       class testclass:
           def mul(s, arg1, arg2): return arg1*arg2
           def add(s, arg1, arg2): return arg1+arg2
           def sub(s, arg1, arg2): return arg1-arg2
           def div(s, arg1, arg2): return arg1/arg2

2. Write a server, testserver.py, that creates one or more instances of the 'testclass', and registers them with the Pyro Name Server.

       import Pyro.naming
       import Pyro.core
       from Pyro.errors import PyroError,NamingError

       import testmod

       ###### testclass Pyro object

       class testclass(Pyro.core.ObjBase, testmod.testclass):
               pass

       ###### main server program

       def main():
               Pyro.core.initServer()
               daemon = Pyro.core.Daemon()
               # locate the NS
               locator = Pyro.naming.NameServerLocator()
               print 'searching for Name Server...'
               ns = locator.getNS()
               daemon.useNameServer(ns)

               # connect a new object implementation (first unregister previous one)
               try:
                       # 'test' is the name by which our object will be known to the outside world
                       ns.unregister('test')
               except NamingError:
                       pass

               # connect new object implementation
               daemon.connect(testclass(),'test')

               # enter the server loop.
               print 'Server object "test" ready.'
               daemon.requestLoop()

       if __name__=="__main__":
               main()

3. To make it interesting, the shortest client possible looks someting like:

       import Pyro.core
       o=Pyro.core.getProxyForURI('PYRONAME://:Default.test')
       print o.mul(5,33)

   ... But for educational purposes, we use the long way around. Read on.
4. Write a client, testclient.py, that will find the Name Server.

       import Pyro.naming, Pyro.core
       from Pyro.errors import NamingError

       # locate the NS
       locator = Pyro.naming.NameServerLocator()
       print 'Searching Name Server...',
       ns = locator.getNS()

   (... continued ...)
5. Let the client query the NS for the object's URI. Then create a proxy for the remote object. Because the proxy appears the same as the real 'testclass', the client can now invoke methods on the remote objects.

   (...continued from above...)

       # resolve the Pyro object
       print 'finding object'
       try:
               URI=ns.resolve('test')
               print 'URI:',URI
       except NamingError,x:
               print 'Couldn\'t find object, nameserver says:',x
               raise SystemExit

       # create a proxy for the Pyro object, and return that
       test = Pyro.core.getProxyForURI(URI)

       print test.mul(111,9)
       print test.add(100,222)
       print test.sub(222,100)
       print test.div(2.0,9.0)
       print test.mul('*',10)
       print test.add('String1','String2')

6. Run the application in the network. First, start the Name Server on one computer.

       irmen@atlantis:~ > pyro-ns
       *** Pyro Name Server ***
       Pyro Server Initialized. Using Pyro V3.7
       URI is: PYRO://10.0.0.150:9090/0a00009604005c6282a8a516d79917fd
       URI written to: e:\Pyro_NS_URI
       Name Server started.

7. Start the server on another computer (or in a different shell).

       irmen@atlantis:~/ex > python testserver.py
       Pyro Server Initialized. Using Pyro V3.5
       searching for Name Server...
       Server object "test" ready.

8. Finally, run the client on a third computer (or in a different shell).

       irmen@atlantis:~/ex > python testclient.py
       Pyro Client Initialized. Using Pyro V3.5
       Searching Name Server... finding object
       URI: PYRO://10.0.0.150:7766/0a0000960c545c62a91e3021bceb7f26
       999
       322
       122
       0.222222222222
       **********
       String1String2

9. You might want to peek in the Name Server:

       irmen@atlantis:~/ex > pyro-nsc listall
       Locator: searching Pyro Name Server...
       NS is at 10.0.0.150 (isengard.lan) port 9090
       -------------- START DATABASE
       :Default.test  -->  PYRO://10.0.0.150:7766/0a0000960c545c62a91e3021bceb7f26
       :Pyro.NameServer  -->  PYRO://10.0.0.150:9090/0a00009604005c6282a8a516d79917fd
       -------------- END

10. And if you're interested you may want to try the logging facility of Pyro. First, set the tracelevel to something other than the default, 0. See the chapter on configuration how to do that. Usually you'll set the environment variable `PYRO_TRACELEVEL` to 3 (=maximum logging). Then, when you start Pyro programs (like the nameserver), they will write something like this to the logfile:

        ------------------------------------------------------------ NEW SESSION
        2005-03-13 13:23:40   Pyro Initializing, version 3.7
        This is initServer.
        Configuration settings are as follows:
        PYRO_BC_RETRIES = 2
        PYRO_BC_TIMEOUT = 2
        PYRO_CHECKSUM = 0
        PYRO_COMPRESSION = 0
        PYRO_CONFIG_FILE =
        PYRO_DETAILED_TRACEBACK = 0
        PYRO_DNS_URI = 0
        PYRO_ES_BLOCKQUEUE = 1
        PYRO_ES_QUEUESIZE = 1000
        PYRO_LOGFILE = E:\temp\Pyro_log
        PYRO_MAXCONNECTIONS = 200
        PYRO_MOBILE_CODE = 0
        PYRO_MULTITHREADED = 1
        PYRO_NS2_BC_PORT = 9091
        PYRO_NS2_HOSTNAME = None
        PYRO_NS2_PORT = 9091
        PYRO_NS_BC_PORT = 9090
        PYRO_NS_DEFAULTGROUP = :Default
        PYRO_NS_HOSTNAME = None
        PYRO_NS_PORT = 9090
        PYRO_NS_URIFILE = E:\temp\Pyro_NS_URI
        PYRO_PICKLE_FORMAT = 2
        PYRO_PORT = 7766
        PYRO_PORT_RANGE = 100
        PYRO_PRINT_REMOTE_TRACEBACK = 0
        PYRO_SOCK_KEEPALIVE = 1
        PYRO_STDLOGGING = 0
        PYRO_STDLOGGING_CFGFILE = logging.cfg
        PYRO_STORAGE = E:\temp
        PYRO_TCP_LISTEN_BACKLOG = 200
        PYRO_TRACELEVEL = 3
        PYRO_USER_LOGFILE = E:\temp\Pyro_userlog
        PYRO_USER_TRACELEVEL = 0
        PYRO_XML_PICKLE = None
        Init done.
        ----------------------------------------------------------------------
        2005-03-13 13:23:44 [1084:MainThread] ** NOTE ** NameServer ** created group :Pyro
        2005-03-13 13:23:44 [1084:MainThread] ** NOTE ** NameServer ** created group :Default
        2005-03-13 13:23:44 [1084:MainThread] ** NOTE ** NameServer ** Running in single mode
        2005-03-13 13:23:44 [1084:MainThread] ** NOTE ** NameServer ** registered NameServer with URI PYRO://10.0.0.150:9090/0a000096043c5c63117eead5b89ea267
        2005-03-13 13:23:44 [1084:MainThread] ** NOTE ** NameServer ** URI written to E:\temp\Pyro_NS_URI
        2005-03-13 13:23:44 [1084:MainThread] ** NOTE ** NS daemon ** This is the Pyro Name Server.
        2005-03-13 13:23:44 [1084:MainThread] ** NOTE ** NS daemon ** Starting on isengard port 9090  broadcast server on port 9090