The socket module doesn't seem to support the sendmsg 
operation for AF_UNIX sockets, at least in Python 2.2.2 
under Linux.  This is needed to send ancillary messages 
to sockets.  Those in turn allow a process to see the 
user id of its peer, allows sending file descriptors to 
other processes (needed for anything like User Mode 
Linux so that non-root processes can open privileged 
ports), and so forth.