'dpid: dpid hex string (or None to derive from name, e.g. s1 -> 1)
opts: additional switch options
listenPort: port to listen on for dpctl connections'

def __init__(self, name, dpid=None, opts='', listenPort=None, **params):

    Node.__init__(self, name, **params)
    self.dpid = self.defaultDpid(dpid)
    self.opts = opts
    self.listenPort = listenPort
    if (not self.inNamespace):
        self.controlIntf = Intf('lo', self, port=0)
