Providing 0 as a port in __init__ of 
SocketServer.TCPServer leads to different values for 
port in server_address and socket.getsockname().

Example:
import SocketServer
s = SocketServer.TCPServer(("0.0.0.0", 0), Handler)
s.server_address
-> ('0.0.0.0', 0)
s.socket.getsockname()
-> ('0.0.0.0', 39129)

s.server_address should also contain 39129 as the 
port number for the free port found.