twisted.names.client.getHostByName() UDP socket leak

New submission from pythonologist <None>:

The utility function twisted.names.client.getHostByName() does not seem to close the UDP socket it opens, resulting over time in a build-up of UDP ports in use. See attached test program dns_test.py.

On Linux you can see the socket count increase via: lsof -i -nP | grep UDP | wc -l
On Windows it runs out of file descriptors after a period of 10 mins or so


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Type     : defect
Component: names
Keywords : 
Priority : normal
Nosy     : 
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http://twistedmatrix.com/trac/ticket/3982