I've tried to run the code below on Windows XP and Linux Ubuntu and it
works as expected. Here is the output:

expt -> o
read -> fo

On FreeBSD 7.0 it raises the following exception:

expt -> o
read -> fo 
Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/local/lib/python2.5/threading.py", line 460, in __bootstrap
    self.run()
  File "/usr/local/lib/python2.5/threading.py", line 440, in run
    self.__target(*self.__args, **self.__kwargs)
  File "_test2.py", line 13, in server
    data = conn.recv(1024, socket.MSG_OOB)
error: (22, 'Invalid argument')





--- code ---

import socket, select, threading, time, os

def server():
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    s.bind(('', 1024))
    s.listen(1)
    conn, addr = s.accept()
    conn.setblocking(0)
    while 1:
        r, w, e = select.select([conn], [conn], [conn], 0.01)
        if e:
            data = conn.recv(1024, socket.MSG_OOB)
            print "expt -> " + data
        if r:
            data = conn.recv(1024)
            print "read -> " + data


threading.Thread(target=server).start()
time.sleep(0.1)
s = socket.socket()
s.connect(('127.0.0.1', 1024))
s.sendall('foo', socket.MSG_OOB)

--- /code ---