'Make sure stopProtocol is called.
This will be called by the port, users should not call it.'

def doStop(self):

    assert (self.numPorts > 0)
    self.numPorts = (self.numPorts - 1)
    self.transport = None
    if (not self.numPorts):
        if self.noisy:
            log.msg(('Stopping    protocol    %s' % self))
        self.stopProtocol()
