'Get the L{Tunnel} object associated with the given L{TuntapPort}.
@param port: A L{TuntapPort} previously initialized using this
L{MemoryIOSystem}.
@return: The tunnel object created by a prior use of C{open} on this
object on the tunnel special device file.
@rtype: L{Tunnel}'

def getTunnel(self, port):

    return self._openFiles[port.fileno()]
