diff -r 5fbf0d010276 Lib/multiprocessing/connection.py
--- a/Lib/multiprocessing/connection.py	Mon Jun 13 14:59:36 2011 +0100
+++ b/Lib/multiprocessing/connection.py	Thu Jun 16 02:04:54 2011 -0400
@@ -186,6 +186,11 @@
         '''
         if duplex:
             s1, s2 = socket.socketpair()
+            # _multiprocessing.Connection read/write semantics do not handle
+            # non-blocking sockets correctly (issue 6056). This bug-fix
+            # retains current behavior and allows for a default socket timeout
+            s1.settimeout(None)
+            s2.settimeout(None)
             c1 = _multiprocessing.Connection(os.dup(s1.fileno()))
             c2 = _multiprocessing.Connection(os.dup(s2.fileno()))
             s1.close()
@@ -250,6 +255,8 @@
     def __init__(self, address, family, backlog=1):
         self._socket = socket.socket(getattr(socket, family))
         self._socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        # non-blocking sockets fix for issue 6056
+        self._socket.settimeout(None)
         self._socket.bind(address)
         self._socket.listen(backlog)
         self._address = self._socket.getsockname()
@@ -265,6 +272,8 @@
 
     def accept(self):
         s, self._last_accepted = self._socket.accept()
+        # non-blocking sockets fix for issue 6056
+        s.settimeout(None)
         fd = duplicate(s.fileno())
         conn = _multiprocessing.Connection(fd)
         s.close()
@@ -282,6 +291,8 @@
     '''
     family = address_type(address)
     s = socket.socket( getattr(socket, family) )
+    # non-blocking sockets fix for issue 6056
+    s.settimeout(None)
     t = _init_timeout()
 
     while 1:
diff -r 5fbf0d010276 Lib/test/test_multiprocessing.py
--- a/Lib/test/test_multiprocessing.py	Mon Jun 13 14:59:36 2011 +0100
+++ b/Lib/test/test_multiprocessing.py	Thu Jun 16 02:04:54 2011 -0400
@@ -2105,6 +2105,10 @@
 
 def main():
     test_main(unittest.TextTestRunner(verbosity=2).run)
+    # run all tests again with non-blocking sockets and positive timeout
+    # see Issue 6056
+    socket.setdefaulttimeout(60)
+    test_main(unittest.TextTestRunner(verbosity=2).run)
 
 if __name__ == '__main__':
     main()
diff -r 5fbf0d010276 Misc/ACKS
--- a/Misc/ACKS	Mon Jun 13 14:59:36 2011 +0100
+++ b/Misc/ACKS	Thu Jun 16 02:04:54 2011 -0400
@@ -879,6 +879,7 @@
 Sue Williams
 Gerald S. Williams
 Frank Willison
+J Derek Wilson
 Greg V. Wilson
 Jody Winston
 Collin Winter
diff -r 5fbf0d010276 Misc/NEWS
--- a/Misc/NEWS	Mon Jun 13 14:59:36 2011 +0100
+++ b/Misc/NEWS	Thu Jun 16 02:04:54 2011 -0400
@@ -16,6 +16,9 @@
 Library
 -------
 
+- Issue #6056: Allow socket.setdefaulttimeout to work with _mutliprocessing
+  socket interface that expects blocking sockets.
+
 - Issue #9284: Allow inspect.findsource() to find the source of doctest
   functions.