Example of opening a UDP socket in a Mininet host and writing the received packets to a file

mininetSocketTest.py

#!/usr/bin/python

from mininet.topo import Topo, SingleSwitchTopo
from mininet.net import Mininet
from mininet.log import lg, info
from mininet.cli import CLI

def main():
    lg.setLogLevel('info')

    net = Mininet(SingleSwitchTopo(k=2))
    net.start()

    h1 = net.get('h1')
    p1 = h1.popen('python myServer.py -i %s &' % h1.IP())

    h2 = net.get('h2')
    h2.cmd('python myClient.py -i %s -m "hello world"' % h1.IP())

    CLI( net )
    p1.terminate()
    net.stop()

if __name__ == '__main__':
    main()

myClient.py

import socket, optparse

parser = optparse.OptionParser()
parser.add_option('-i', dest='ip', default='127.0.0.1')
parser.add_option('-p', dest='port', type='int', default=12345)
parser.add_option('-m', dest='msg')
(options, args) = parser.parse_args()

s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.sendto(options.msg, (options.ip, options.port) )

myServer.py

import socket, optparse

parser = optparse.OptionParser()
parser.add_option('-i', dest='ip', default='')
parser.add_option('-p', dest='port', type='int', default=12345)
(options, args) = parser.parse_args()

s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.bind( (options.ip, options.port) )

f = open('foo.txt','w')
while True:
  data, addr = s.recvfrom(512)
  f.write("%s: %s\n" % (addr, data))
  f.flush()

my ubuntu has only python3 installed. Is that why my foo.txt is empty?