pox sdn mininet，计算udp数据包

Question

我想计算使用pox和openflow切换的UDP数据包的数量 这是我使用的拓扑：

#!/usr/bin/python

"""
Script created by VND - Visual Network Description (SDN version)
"""
from mininet.net import Mininet
from mininet.node import Controller, RemoteController, OVSKernelSwitch, IVSSwitch, UserSwitch
from mininet.link import Link, TCLink
from mininet.cli import CLI
from mininet.log import setLogLevel

def topology():

    "Create a network."
    net = Mininet( controller=Controller, link=TCLink, switch=OVSKernelSwitch )

    print "*** Creating nodes"
    c1 = net.addController( 'c1' )
    s2 = net.addSwitch( 's2', protocols='OpenFlow13', listenPort=6673, mac='00:00:00:00:00:02' )
    h4 = net.addHost( 'h4', mac='00:00:00:00:00:04', ip='10.0.0.4/8' )
    h5 = net.addHost( 'h5', mac='00:00:00:00:00:05', ip='10.0.0.5/8' )
    h6 = net.addHost( 'server', mac='00:00:00:00:00:06', ip='10.0.0.6/8' )

    print "*** Creating links"
    net.addLink(s2, h6)
    net.addLink(s2, h4)
    net.addLink(s2, h5)

    print "*** Starting network"
    net.build()
    c1.start()
    s2.start( [c1] )

    print "*** Running CLI"
    CLI( net )

    print "*** Stopping network"
    net.stop()

if __name__ == '__main__':
    setLogLevel( 'info' )
    topology()

我想计算“h4”通过交换机发送给服务器的udp数据包的数量，以及“h5”通过交换机发送给服务器的udp数据包的数量。