examples/ping-pong.py: getting IOError when using 'real' sockets instead of Fake streams

[thekorn]

I'm trying to find out how python-xmpp-server works by looking at the examples.
ping-pong.py works fine, as long as I use the Fake stream, but when I comment these three lines, and uncomment the xmpp.{TCPServer,TCPClient} lines I get an IOError:

diff --git a/examples/ping-pong.py b/examples/ping-pong.py
index 75f9f6f..c5100d5 100644
--- a/examples/ping-pong.py
+++ b/examples/ping-pong.py
@@ -154,11 +154,11 @@ if __name__ == '__main__':
         'keyfile': os.path.join(os.path.dirname(__file__), 'certs/self.key')
     })

-    CP = Stream('C', client, lambda d: SP.reader(d))
-    SP = Stream('S', server, lambda d: CP.reader(d))
-    Stream.loop()
+    #~ CP = Stream('C', client, lambda d: SP.reader(d))
+    #~ SP = Stream('S', server, lambda d: CP.reader(d))
+    #~ Stream.loop()

-    # SP = xmpp.TCPServer(server).bind('127.0.0.1', '9000')
-    # CP = xmpp.TCPClient(client).connect('127.0.0.1', '9000')
-    # xmpp.start([SP, CP])
+    SP = xmpp.TCPServer(server).bind('127.0.0.1', '9000')
+    CP = xmpp.TCPClient(client).connect('127.0.0.1', '9000')
+    xmpp.start([SP, CP])

% python examples/ping-pong.py
ERROR:root:TCPClient: error while handling WRITE
Traceback (most recent call last):
  File "/home/markus/.local/lib/python2.7/site-packages/xmpp/aio.py", line 148, in _ready
    self.handler(self.socket, self.address, self.io)
  File "/home/markus/.local/lib/python2.7/site-packages/xmpp/xmppstream.py", line 60, in __call__
    stream = readstream.ReadStream(socket, io_loop, **kwargs)
  File "/home/markus/.local/lib/python2.7/site-packages/xmpp/readstream.py", line 28, in __init__
    self.io.add_handler(socket.fileno(), self._handle, self._state)
  File "/usr/lib/pymodules/python2.7/tornado/ioloop.py", line 149, in add_handler
    self._impl.register(fd, events | self.ERROR)
IOError: [Errno 17] File exists

% python --version
Python 2.7.1+
(package on ubuntu 11.04)

Tell me if I can provide further information.
Thanks in advance,
Markus