t.test.test_ftp.FTPServerPortDataConnectionTestCase.testManyLargeDownloads fails with iocpreactor/Vista

New submission from ivank <[email protected]>:

`twisted.test.test_ftp.FTPServerPortDataConnectionTestCase.testManyLargeDownloads` fails after just a few runs with iocpreactor on Server 2008 SP1 (probably Vista, probably Windows 7)

This is almost certainly due to bug #3233 "twisted.test.test_tcp.LargeBufferTestCase.testWriter fails with iocp reactor"

{{{
C:\temp\temp3>python C:\Python26\Scripts\trial.py -u -r iocp twisted.test.test_ftp.FTPServerPortDataConnectionTestCase.testManyLargeDownloads
Test Pass 1
twisted.test.test_ftp
  FTPServerPortDataConnectionTestCase
    testManyLargeDownloads ...                                             [OK]

-------------------------------------------------------------------------------
Ran 1 tests in 0.121s

PASSED (successes=1)
Test Pass 2
twisted.test.test_ftp
  FTPServerPortDataConnectionTestCase
    testManyLargeDownloads ...                                           [FAIL]

===============================================================================
[FAIL]: twisted.test.test_ftp.FTPServerPortDataConnectionTestCase.testManyLargeDownloads

Traceback (most recent call last):
  File "C:\Python26\lib\site-packages\twisted\test\test_ftp.py", line 492, in checkDownload
    self.assertEqual('x' * size, download)
twisted.trial.unittest.FailTest: not equal:
a = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
...traceback elided, it is far too long...
}}}

I tested with Python 2.6.2 32 bit, Twisted r27226

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Type     : defect
Component: ftp
Keywords : 
Priority : normal
Nosy     : 
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http://twistedmatrix.com/trac/ticket/3965