Problem running twisted.words example using msn protocol

Question

I am currently trying to use the Twisted library specifically twisted words to try and interat with MSN. However when i run the sample script provided by twisted , i get an error. Specifically the error is found here http://i42.tinypic.com/wl945w.jpg . The script can be found over here http://twistedmatrix.com/projects/words/documentation/examples/msn_example.py.

Platform is Vista with Python 2.6

EDIT: Full output:

Email (passport): [email protected]
Password: ******
2009-04-25 10:52:49-0300 [-] Log opened.
2009-04-25 10:52:49-0300 [-] Starting factory <twisted.internet.protocol.ClientFactory instance at 0x9d87e8c>
2009-04-25 10:52:55-0300 [Dispatch,client] Starting factory <twisted.words.protocols.msn.NotificationFactory instance at 0x9e28bcc>
2009-04-25 10:52:55-0300 [Dispatch,client] Stopping factory <twisted.internet.protocol.ClientFactory instance at 0x9d87e8c>
2009-04-25 10:52:55-0300 [Notification,client] Unhandled Error
    Traceback (most recent call last):
      File "/usr/local/lib/python2.5/site-packages/twisted/python/log.py", line 84, in callWithLogger
        return callWithContext({"system": lp}, func, *args, **kw)
      File "/usr/local/lib/python2.5/site-packages/twisted/python/log.py", line 69, in callWithContext
        return context.call({ILogContext: newCtx}, func, *args, **kw)
      File "/usr/local/lib/python2.5/site-packages/twisted/python/context.py", line 59, in callWithContext
        return self.currentContext().callWithContext(ctx, func, *args, **kw)
      File "/usr/local/lib/python2.5/site-packages/twisted/python/context.py", line 37, in callWithContext
        return func(*args,**kw)
    --- <exception caught here> ---
      File "/usr/local/lib/python2.5/site-packages/twisted/internet/selectreactor.py", line 146, in _doReadOrWrite
        why = getattr(selectable, method)()
      File "/usr/local/lib/python2.5/site-packages/twisted/internet/tcp.py", line 460, in doRead
        return self.protocol.dataReceived(data)
      File "/usr/local/lib/python2.5/site-packages/twisted/protocols/basic.py", line 238, in dataReceived
        why = self.lineReceived(line)
      File "/usr/local/lib/python2.5/site-packages/twisted/words/protocols/msn.py", line 651, in lineReceived
        handler(params.split())
      File "/usr/local/lib/python2.5/site-packages/twisted/words/protocols/msn.py", line 827, in handle_USR
        d = _login(f.userHandle, f.password, f.passportServer, authData=params[3])
      File "/usr/local/lib/python2.5/site-packages/twisted/words/protocols/msn.py", line 182, in _login
        reactor.connectSSL(_parsePrimitiveHost(nexusServer)[0], 443, fac, ClientContextFactory())
    exceptions.TypeError: 'NoneType' object is not callable

2009-04-25 10:52:55-0300 [Notification,client] Stopping factory <twisted.words.protocols.msn.NotificationFactory instance at 0x9e28bcc>

Answer 1

What happened

This exception you get is when you try to call an object that is None. Check this out :

>>> a = str
>>> a() # it's ok, a string is a callable class
''
>>> a = None
>>> a() # it fails, None a special Singleton not meant to be called

Traceback (most recent call last):
  File "<pyshell#4>", line 1, in <module>
    a()
TypeError: 'NoneType' object is not callable

What you can do

You can't guess it like that, so you'll need to make some debugging.

Apparently, the last line (refactor.connectSSL...) contains three object calls, and one of the object is None.

The first thing you can do, if you are not into debuggers, if to take each element of the line and add, just before it :

assert object1 is None 
assert object2 is None

Then you'll have the source of your Exception. After that, check why is this object set to None. You'll probably have to check the doc to see in which case some method that may have initilized it returns None.

May the force...

Answer 2

Since MSN involves SSL connections, you must have pyOpenSSL installed in order to use it. It seems as though you probably do not. This isn't a very good way for Twisted to be reporting this missing dependency, though. I recommend filing a ticket in the Twisted issue tracker for improving this reporting.