homepage

[Updating the issue with relevant mailing list conversation]
Interesting results! I committed the patch to test_socket.py in 
r62152. I was expecting all other platforms except for Windows to 
behave consistently (i.e. pass). That is, given the following:
 import socket
 host = '127.0.0.1'
 sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
 sock.bind((host, 0))
 port = sock.getsockname()[1]
 sock.close()
 del sock
 sock1 = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
 sock1.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 sock1.bind((host, port))
 sock2 = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
 sock2.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 sock2.bind((host, port))
 ^^^^
....the second bind should fail with EADDRINUSE, at least according to 
the 'SO_REUSEADDR and SO_REUSEPORT Socket Options' section in chapter 
7.5 of Stevens' UNIX Network Programming Volume 1 (2nd Ed):
"With TCP, we are never able to start multiple servers that bind
 the same IP address and same port: a completely duplicate binding.
 That is, we cannot start one server that binds 198.69.10.2 port 80
 and start another that also binds 198.69.10.2 port 80, even if we
 set the SO_REUSEADDR socket option for the second server."
The results: both Windows *and* Linux fail the patched test; none of 
the buildbots for either platform encountered an EADDRINUSE 
socket.error after the second bind(). FreeBSD, OS X, Solaris and Tru64 
pass the test -- EADDRINUSE is raised on the second bind. (Interesting 
that all the ones that passed have a BSD lineage.)
I've just reverted the test in r62156 as planned. The real issue now 
is that there are tests that are calling test_support.bind_socket() 
with the assumption that the port returned by this method is 'unbound', 
when in fact, the current implementation can't guarantee this:
def bind_port(sock, host='', preferred_port=54321):
 for port in [preferred_port, 9907, 10243, 32999, 0]:
 try:
 sock.bind((host, port))
 if port == 0:
 port = sock.getsockname()[1]
 return port
 except socket.error, (err, msg):
 if err != errno.EADDRINUSE:
 raise
 print >>sys.__stderr__, \
 ' WARNING: failed to listen on port %d, trying 
another' % port
This logic is only correct for platforms other than Windows and Linux. 
I haven't looked into all the networking test cases that rely on 
bind_port(), but I would think an implementation such as this would be 
much more reliable than what we've got for returning an unused port:
def bind_port(sock, host='127.0.0.1', *args):
 s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
 s.bind((host, 0))
 port = s.getsockname()[1]
 s.close()
 del s
 sock.bind((host, port))
 return port
Actually, FWIW, I just ran a full regrtest.py against trunk on Win32 
with this change in place and all the tests still pass.
Thoughts?
 Trent.