This fixes issue 4332 for Py3k.

josiahcarlson · josiahcarlson · commit aae55cbab41a · 2008-11-19T18:22:41.000Z
diff --git a/Lib/asyncore.py b/Lib/asyncore.py
@@ -614,6 +614,6 @@ def __init__(self, fd, map=None):
             fcntl.fcntl(fd, fcntl.F_SETFL, flags)
 
         def set_file(self, fd):
-            self._fileno = fd
             self.socket = file_wrapper(fd)
+            self._fileno = self.socket.fileno()
             self.add_channel()
