examples: adding some basic examples

 * consumer/producer
 * ndnping
 * traffic generator
 * catchunks/putchunks

Change-Id: Ie4c37f08f29a945f2fb1ce0b4d36da1bfb3edd3b
diff --git a/examples/ping-demo.py b/examples/ping-demo.py
new file mode 100644
index 0000000..550c0df
--- /dev/null
+++ b/examples/ping-demo.py
@@ -0,0 +1,109 @@
+# -*- Mode:python; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+#
+# Copyright (C) 2015-2021, The University of Memphis,
+#                          Arizona Board of Regents,
+#                          Regents of the University of California.
+#
+# This file is part of Mini-NDN.
+# See AUTHORS.md for a complete list of Mini-NDN authors and contributors.
+#
+# Mini-NDN is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Mini-NDN is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Mini-NDN, e.g., in COPYING.md file.
+# If not, see <http://www.gnu.org/licenses/>.
+
+from subprocess import PIPE
+
+from mininet.log import setLogLevel, info
+from mininet.topo import Topo
+
+from minindn.minindn import Minindn
+from minindn.apps.app_manager import AppManager
+from minindn.util import MiniNDNCLI, getPopen
+from minindn.apps.nfd import Nfd
+from minindn.helpers.nfdc import Nfdc
+
+PREFIX = "/example"
+
+def printOutput(output):
+    _out = output.decode("utf-8").split("\n")
+    for _line in _out:
+        info(_line + "\n")
+
+def run():
+    Minindn.cleanUp()
+    Minindn.verifyDependencies()
+
+    # Topology can be created/modified using Mininet topo object
+    topo = Topo()
+    info("Setup\n")
+    # add hosts
+    a = topo.addHost('a')
+    b = topo.addHost('b')
+    c = topo.addHost('c')
+
+    # add links
+    topo.addLink(a, b, delay='10ms', bw=10) # bw = bandwidth
+    topo.addLink(b, c, delay='10ms', bw=10)
+
+    ndn = Minindn(topo=topo)
+    ndn.start()
+
+    # configure and start nfd on each node
+    info("Configuring NFD\n")
+    AppManager(ndn, ndn.net.hosts, Nfd, logLevel="DEBUG")
+
+    """
+    There are multiple ways of setting up routes in Mini-NDN
+    refer: https://minindn.memphis.edu/experiment.html#routing-options
+    It can also be set manually as follows. The important bit to note here
+    is the use of the Nfdc command
+    """
+    links = {"a":["b"], "b":["c"]}
+    for first in links:
+        for second in links[first]:
+            host1 = ndn.net[first]
+            host2 = ndn.net[second]
+            interface = host2.connectionsTo(host1)[0][0]
+            interface_ip = interface.IP()
+            Nfdc.createFace(host1, interface_ip)
+            Nfdc.registerRoute(host1, PREFIX, interface_ip, cost=0)
+
+    # Start ping server
+    info("Starting pings...\n")
+    pingserver_log = open("/tmp/minindn/c/ndnpingserver.log", "w")
+    getPopen(ndn.net["c"], "ndnpingserver {}".format(PREFIX), stdout=pingserver_log,\
+             stderr=pingserver_log)
+
+    # start ping client
+    ping1 = getPopen(ndn.net["a"], "ndnping {} -c 5".format(PREFIX), stdout=PIPE, stderr=PIPE)
+    ping1.wait()
+    printOutput(ping1.stdout.read())
+
+    interface = ndn.net["b"].connectionsTo(ndn.net["a"])[0][0]
+    info("Failing link\n") # failing link by setting link loss to 100%
+    interface.config(delay="10ms", bw=10, loss=100)
+    info ("\n starting ping2 client \n")
+
+    ping2 = getPopen(ndn.net["a"], "ndnping {} -c 5".format(PREFIX), stdout=PIPE, stderr=PIPE)
+    ping2.wait()
+    printOutput(ping2.stdout.read())
+
+    interface.config(delay="10ms", bw=10, loss=0) # bringing back the link
+
+    info("\nExperiment Completed!\n")
+    MiniNDNCLI(ndn.net)
+    ndn.stop()
+
+if __name__ == '__main__':
+    setLogLevel("info")
+    run()
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