What steps will reproduce the problem?  
1. Set up a common FTP server.
2. Connect with a client and send a command using OOB (urgent) data (e.g.
ABOR or STAT commands).

A discussion about this issue has been raised on the list: 
http://groups.google.com/group/pyftpdlib/browse_thread/thread/9a54f4f22c0609f0 

What is the expected output?  


What do you see instead?  
The server prints the following message disconnecting the client.

[test]@x:52291 Can't handle OOB data.
[test]@x:52291 Disconnected. 

The reason for that is that when we try to read OOB data on FreeBSD an
EINVAL error is raised.
A read at Unix Network Programming third edition reveals that this is the
expected behavior:

"4. If the process has set the SO_OOBINLINE socket option and then tries
to read the out-of-band data by specifying MSG_OOB, EINVAL is returned."

The patch in attachment modifies ftpserver.py so that SO_OOBINLINE option
is set against the command channel's socket and if reading OOB data from
the socket results in an EINVAL error we just pass on.