Open telnet connection

        Args:
            params (dict), must contain two parameters "ip" - ip address or hostname and "port" - port number

        Example:
            params = {'port': 23, 'ip': 'localhost'}

def open(self, **params):
        """Open telnet connection

        Args:
            params (dict), must contain two parameters "ip" - ip address or hostname and "port" - port number

        Example:
            params = {'port': 23, 'ip': 'localhost'}
        """
        logger.info('opening telnet')
        self.port = params['port']
        self.ip = params['ip']
        self.tn = None
        self._init()