软件定义网络入门学习笔记3-学习第一个ryu应用

    from ryu.base import app_manager
    from ryu.controller import ofp_event
    from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER
    from ryu.controller.handler import set_ev_cls
    from ryu.ofproto import ofproto_v1_3
    from ryu.lib.packet import packet
    from ryu.lib.packet import ethernet
    from ryu.lib.packet import ether_types
    
    
    class SimpleSwitch13(app_manager.RyuApp):
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]
    
    def __init__(self, *args, **kwargs):
        super(SimpleSwitch13, self).__init_